Create ONBOARDING.md

[anandtiwary]

Description

Please include a summary of the change, motivation and context.
This document will contain information that would help onboard new contributors with hypertrace-ui. This is the first iteration.

Testing

Please describe the tests that you ran to verify your changes. Please summarize what did you test and what needs to be tested e.g. deployed and tested helm chart locally.

Checklist:

• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• Any dependent changes have been merged and published in downstream modules

Documentation

Make sure that you have documented corresponding changes in this repository or hypertrace docs repo if required.

[codecov]

Codecov Report

Merging #836 (00aaa45) into main (f15cb7e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #836   +/-   ##
=======================================
  Coverage   85.44%   85.44%           
=======================================
  Files         793      793           
  Lines       16252    16252           
  Branches     1932     1932           
=======================================
  Hits        13886    13886           
  Misses       2334     2334           
  Partials       32       32           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f15cb7e...00aaa45. Read the comment docs.

[github-actions]

Unit Test Results

    4 files  ±0  250 suites  ±0   14m 33s ⏱️ +2s
899 tests ±0  899 ✔️ ±0  0 💤 ±0  0 ❌ ±0 
905 runs  ±0  905 ✔️ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit afa5bd7. ± Comparison against base commit f15cb7e.