docs: Add Typescript instructions to Contributing guide

[dplewis]

Pull Request

• Report security issues confidentially.
• Any contribution is under this license.
• Link this pull request to an issue.

Issue

Typescript instructions are missing.

Approach

• Move and rename tests.ts to Parse-test.ts
• Expand tests to include multiple test files.

Tasks

• Add tests
• Add changes to documentation (guides, repository pages, code comments)

[parse-github-assistant]

Thanks for opening this pull request!

• ❌ Please link an issue that describes the reason for this pull request, otherwise your pull request will be closed. Make sure to write it as Closes: #123 in the PR description, so I can recognize it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (a929019) to head (4d9809b).

Additional details and impacted files

@@            Coverage Diff            @@
##             alpha     #2463   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           64        64           
  Lines         6256      6256           
  Branches      1451      1447    -4     
=========================================
  Hits          6256      6256           

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