docs: update language option documentaion

[MkMan]

In this PR:

• Update documentation for language to match the example provided
• Fix spacing, numbering, TOC in CONTRIBUTING.md

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Fixes #160 🦕

[codecov]

Codecov Report

Merging #161 (b881dc5) into master (2bccb7d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #161   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          118       118           
  Branches        24        24           
=========================================
  Hits           118       118           

Impacted Files	Coverage Δ
src/index.ts	100.00% <ø> (ø)

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[github-actions]

🎉 This PR is included in version 1.11.2 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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