add thai language

Thanks a lot for your contribution! Could you please follow the documentation link https://remark42.com/docs/contributing/translations/ to alter other files that need to be changed when you're adding the new language, and test it? Unfortunately, the language won't be available in the web interface with the current state of the PR.

If you can't, it's not a problem; I can merge your changes and do the rest of the work myself.

Nevermind, I found your other PR. It's good to go, and we'll merge it shortly. Thank you!

Codecov Report

Merging #1485 (73d0df0) into master (499302c) will not change coverage.
The diff coverage is n/a.

❗ Current head 73d0df0 differs from pull request most recent head be82e01. Consider uploading reports for the commit be82e01 to get more accurate results

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  Files         131      131           
  Lines        2909     2909           
  Branches      743      743           
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  Hits         1691     1691           
  Misses       1214     1214           
  Partials        4        4           

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thx