Auto-generate the CHANGELOG.md file upon release

[thinkingserious]

Issue Summary

For every release, we currently hand craft a CHANGELOG.md update, now we would like to automate this process. Please see the existing CHANGELOG.md for formatting structure.

Acceptance Criteria

• A script, which when run, creates a CHANGELOG.md update based on any merged PRs since the last release.

[mauricetmeyer]

I would take a look when I have some time later today.

Edit: @thinkingserious I've now got to the point where I generate the markdown file, I was just wondering how you would determine if it's listed under fixed/added/changed. My idea was to look for keywords in a simple way, as closes/fixes is already in the PR template. I could also scan the commit messages linked to the PR or the PR title.

Edit #2: SCREENSHOT