[DOP-13156] - add changelog section

[maxim-lixakov]

Change Summary

• Add changelog section to documentation. Update contributing guide with full release process.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[maxim-lixakov]

Поправил команды:
Remove content above the version number heading in the ${VERSION}.rst file
sed -i '' "0,/^.*towncrier release notes start/d" "docs/changelog/${VERSION}.rst"

Update Changelog Index
sed -i '' -E "s/DRAFT/DRAFT\n ${VERSION}/" "docs/changelog/index.rst"

из последнего шаблона в onetl, так как на MacOS они отличаются

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.62%. Comparing base (3b66c35) to head (0388fbd).
Report is 52 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop      #10   +/-   ##
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  Coverage    96.62%   96.62%           
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  Files            3        3           
  Lines           89       89           
  Branches         8        8           
========================================
  Hits            86       86           
  Misses           3        3           

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[dolfinus]

Добавь в .github/workflows/release.yml шаги с конвертацией changelog в markdown, можно утащить например из onetl