Fix "too many open files" on MacOS

Patch borrowed from sass/libsass#3183 by @tom-un

See See gohugoio/hugo#12649

github: Fix build on Windows

Run gofumpt -l -w ., remove vet and lint check in GitHub action

Merge pull request #4 from bep/update-3.6.5

Update to LibSASS 3.6.5

Merge pull request #3 from bep/libsass364

Update to Libsass 3.6.4

Merge pull request #2 from anthonyfok/fix-internal-libsass-permissions

Change file mode of internal/libsass/* from 0755 to 0644

Merge pull request #1 from bep/fix-imp2

Fix type handling for import resolver

Fix the custom import logic

Add ParseOutputStyle

Add readme note