[cargo smart-release] Changelog generation

[Byron]

Now that it's easier than ever to publish a big amount of crates and do so safely for downstream users, it's absolutely crucial to unify and automate changelog generation.

git-cliff is quite inspirational for showing it is possible, and git-conventional is quite easy to work with and common enough to adopt (with adjustments) to generate valuable change logs automatically.

This should be done in a minimally configurable way only, while making 'debugging' feasible to understand why a piece of information might be missing.

Lastly, it should be possible to hand-edit changelogs and keep them save from future adjustments.

To not re-invent the wheel, we will simply stick to keep-a-changelog as closely as possible.

• dev
• bat changelog generation recording
• write changelog and update readme
• record release of smart-release and redo asciinema recording