docs: Add file extensions to SUPPORTED_LANGUAGES

[ianlewis]

Description:

Add supported file extensions to SUPPORTED_LANGUAGES.md

Related Issues:

Fixes #758

Checklist:

• Review the CONTRIBUTING.md documentation.
• Add a reference to a related issue in the repository.
• Add a description of the changes proposed in the pull request.
• Add unit tests if applicable.
• Update documentation if applicable.
• Add a note in the CHANGELOG.md if applicable.
• Sign the Google CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.81%. Comparing base (cbc2d3f) to head (bdb7dd8).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1501      +/-   ##
==========================================
+ Coverage   78.69%   78.81%   +0.11%     
==========================================
  Files          15       15              
  Lines         892      892              
==========================================
+ Hits          702      703       +1     
+ Misses        139      138       -1     
  Partials       51       51              

see 1 file with indirect coverage changes