Update for release description in gh pages branch

0. during release gh-pages is already cloned.

1. Switch to gh-pages

cd gh-pages

2. Get latest changes from upstream repository

git pull origin gh-pages

3. do MANUAL changes in index.html . Validate rendering on your local

4. commit changes

git add index.html
git status
git commit -m "doc: add release notes for $NEW_VERSION"

6. push changes

git push origin gh-pages

7. validate rendering at http://sevntu-checkstyle.github.io/sevntu.checkstyle/