adding javalin-htmx examples to server integration examples

[ludicrousdisplay]

Adding two examples of using htmx and java with the javalin server library

Description

Adding two server-integration examples for java. Both of these examples use javalin and present a simpler approach to getting started with htmx and java than the current examples which use Spring Boot and Quarkus.

Corresponding issue:

#3099

Testing

I have reviewed a preview of my edits to this file.

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• [NA] I ran the test suite locally (npm run test) and verified that it succeeded

[Telroshan]

I'm not sure what strategy we use to order examples in that page, might be as simple as a "first come first served" so I can't tell you for sure about the order