release: prepare openfeature 0.2.0

[github-actions]

Release openfeature 0.2.0

This PR prepares the openfeature module for release.

Changes

• Bumps version to 0.2.0 (in openfeature-provider/pyproject.toml and/or its referenced version file)
• Updates openfeature-provider/CHANGELOG.md with a new section since the last openfeature/v* tag
• Updates openfeature-provider/README.md version header

After merging

1. Push tag openfeature/v0.2.0 from the merge commit on master to trigger the publish workflow:

   git checkout master && git pull
   git tag openfeature/v0.2.0
   git push origin openfeature/v0.2.0
   

2. The publish workflow creates a draft GitHub release and publishes to PyPI via Trusted Publishing. Review and publish the GitHub release after the workflow finishes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.25%. Comparing base (0f9de4b) to head (4add5f7).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #188   +/-   ##
=======================================
  Coverage   96.25%   96.25%           
=======================================
  Files          13       13           
  Lines        2616     2616           
  Branches      139      139           
=======================================
  Hits         2518     2518           
  Misses         64       64           
  Partials       34       34           

Flag	Coverage Δ
openfeature-provider	54.06% <ø> (ø)

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