bump version to 0.2.0

[sonichi]

Why are these changes needed?

For release.

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6087b5a) 27.69% compared to head (e284b9b) 37.30%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #758      +/-   ##
==========================================
+ Coverage   27.69%   37.30%   +9.61%     
==========================================
  Files          27       27              
  Lines        3466     3479      +13     
  Branches      784      788       +4     
==========================================
+ Hits          960     1298     +338     
+ Misses       2434     2061     -373     
- Partials       72      120      +48     

Flag	Coverage Δ
unittests	37.25% <100.00%> (+9.55%)	⬆️

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[sonichi]

Hi all, I plan to release v0.2 after this PR is merged as users have been asking. Please let me know if there is any breaking change you are working on and would like to hold the release.