Add changelog check for pull requests

[2ykwang]

Require pull requests to update CHANGELOG.md unless the skip-changelog label is applied.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.66%. Comparing base (10ba748) to head (cba7486).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #837      +/-   ##
==========================================
+ Coverage   96.33%   96.66%   +0.33%     
==========================================
  Files          35       35              
  Lines        1256     1321      +65     
==========================================
+ Hits         1210     1277      +67     
+ Misses         46       44       -2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.