* Update versions for release 4
* Link validation file should ignore itself
* Remove 'unreleased' section from changelog
* Change to 0.18.0 for python versions
* also update extensions package version
Co-authored-by: Chris Elion <chris.elion@unity3d.com>
- updated release tag validation script to automate the updating of files with release tags that need to be changed as part of the pre-commit operation.