Add breaking changes to GitHub release notes

The release notes on GitHub are currently empty. It would be beneficial if these contained the breaking changes for each major release. Currently these are only showing in the github repo.

This is about hooking into the release scripts and pushing the changes to the Github releases using the Github API. Start by investigating how the release script works by looking at the scripts in package.json and then how to extract the relevant parts from the changelog markdown file. The github API is quite easy to grok.