feat: migrate to ESM and update dependencies

[v-chiranjib-swain]

Description:
This PR migrates the project to full ESM and modernizes the tooling to align with the latest @actions/* package ecosystem.

Changes

• Migrated the project to ESM.
• Updated dependencies to their latest compatible versions.
• Converted tooling and configuration (ESLint, Prettier, Jest) for ESM.
• Refactored imports, tests, and project structure for ESM compatibility.
• Removed deprecated files and unnecessary mocks.
• Updated the README to document the breaking changes introduced in v7.

Related issue:
Add link to the related issue.

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[Copilot]

Pull request overview

This PR migrates the action’s codebase and tooling from CommonJS to full ESM, aligning with newer @actions/*/Octokit packages and updating the project’s lint/test/format setup to match.

Changes:

• Switched TypeScript compilation to NodeNext/ES2022 and updated all internal imports/exports for ESM (explicit .js specifiers).
• Modernized tooling (ESLint flat config, Prettier config format) and upgraded dependencies for Node 24+.
• Refactored Jest tests to use ESM-compatible mocking (jest.unstable_mockModule) and updated documentation/versioning for the v7 breaking change.

Reviewed changes

Copilot reviewed 55 out of 60 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tsconfig.json	Updates TS output/module settings for ESM (NodeNext) and ES2022 target.
src/main.ts	Updates entrypoint import to ESM-style .js specifier.
src/labeler.ts	Refactors internal imports for ESM and improves error rethrowing with cause.
src/get-inputs/index.ts	Updates barrel export to ESM-style .js specifier.
src/get-inputs/get-inputs.ts	Updates internal import to ESM-style .js specifier.
src/changedFiles.ts	Updates internal import to ESM-style .js specifier.
src/api/set-labels.ts	Updates internal import to ESM-style .js specifier.
src/api/index.ts	Updates API barrel exports to ESM-style .js specifiers.
src/api/get-label-configs.ts	Updates internal imports to ESM-style .js specifiers.
src/api/get-content.ts	Updates internal import to ESM-style .js specifier.
src/api/get-changed-pull-requests.ts	Updates internal imports to ESM-style .js specifiers.
src/api/get-changed-files.ts	Updates internal import to ESM-style .js specifier.
README.md	Documents the v7 breaking change (ESM migration).
package.json	Bumps to v7, sets "type":"module", updates deps, and adjusts scripts for the new toolchain.
jest.config.ts	Introduces Jest configuration in TypeScript for ESM + ts-jest.
jest.config.js	Removes legacy CommonJS Jest configuration.
eslint.config.mjs	Adds ESLint flat config suitable for ESM/TypeScript.
dist/package.json	Marks the bundled dist/ output as ESM.
.prettierrc.json	Adds JSON-based Prettier config (replacing JS config).
.prettierrc.js	Removes legacy CommonJS Prettier config.
.licenses/npm/wrappy.dep.yml	Removes license metadata for a removed dependency.
.licenses/npm/universal-user-agent.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/once.dep.yml	Removes license metadata for a removed dependency.
.licenses/npm/json-with-bigint.dep.yml	Adds license metadata for a newly added dependency.
.licenses/npm/js-yaml.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/deprecation.dep.yml	Removes license metadata for a removed dependency.
.licenses/npm/content-type.dep.yml	Adds license metadata for a newly added dependency.
.licenses/npm/brace-expansion.dep.yml	Updates license metadata version info.
.licenses/npm/before-after-hook.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/types.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/types-13.8.0.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/types-13.10.0.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/types-12.6.0.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/request.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/request-error.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/plugin-retry.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/plugin-rest-endpoint-methods.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/plugin-paginate-rest.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/openapi-types.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/openapi-types-24.2.0.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/openapi-types-23.0.1.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/openapi-types-19.0.1.dep.yml	Removes license metadata for an older pinned version entry.
.licenses/npm/@octokit/graphql.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/endpoint.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/core.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@octokit/auth-token.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@actions/io.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@actions/http-client-4.0.1.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@actions/github.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@actions/exec.dep.yml	Updates license metadata to match updated dependency version.
.licenses/npm/@actions/core.dep.yml	Updates license metadata to match updated dependency version.
.eslintrc.js	Removes legacy .eslintrc configuration in favor of flat config.
.eslintignore	Removes legacy ignore file (handled via flat config ignores).
tests/main.test.ts	Converts tests to ESM-safe mocking/import patterns.
tests/labeler.test.ts	Converts tests to ESM-safe mocking/import patterns and updates imports/types.
tests/changedFiles.test.ts	Converts tests to ESM-safe mocking/import patterns and updates imports/types.
tests/branch.test.ts	Converts tests to ESM-safe mocking/import patterns and updates imports/types.
mocks/@actions/github.ts	Removes legacy Jest manual mock file (replaced by ESM mocking).

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