The handbook is a moving target, and keeping up is really hard. To
mitigate this, we could leverage a git tag and view diffs. But that
creates large blobs that contains stuff I'm not interested in.

This commmits introduces a way to generate the changelog, which after
merging should allow us to generate/update it.

This is a first iteration, and misses good styles for example. But given
its also an experiment, the current iteration should be enough.