Document how to debug unit tests in VSCode

[RISHIKESHk07]

…ts in README.md

Which problem is this PR solving?

Resolve #2118

Description of the changes

• Added a launch json in the README.md which explains how to set the debugger of vscode to test unit tests with jest.

How was this change tested?

• Proof of work was present in the comment thread of the issue Find out and document how to debug unit tests from VSCode #2118

Checklist

• I have read https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
• I have signed all commits
• [] I have added unit tests for the new functionality
• [] I have run lint and test steps successfully
  • for jaeger: make lint test
  • for jaeger-ui: yarn lint and yarn test

[yurishkuro]

🎉

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.60%. Comparing base (926f454) to head (c13d4b9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2297   +/-   ##
=======================================
  Coverage   96.60%   96.60%           
=======================================
  Files         254      254           
  Lines        7662     7662           
  Branches     1996     1994    -2     
=======================================
  Hits         7402     7402           
  Misses        260      260           

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