feat: allow custom notes in body text

[btkostner]

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Fixes #1274

This allows setting up custom notes in release changelogs as described in #1274. It does so by parsing magic strings in the commit message and setting the parsed text as a note. Because we are pigging back off notes, support for rendering this information is already done. Let me know how you feel about this approach and I can update as needed.

[btkostner]

I just realized that the template will not render these notes like I want. I’ll update and add more tests in that area.

[chingor13]

I’ll update and add more tests in that area.

If you ever get back to this, feel free to re-open. The annotations used might warrant more discussion in the feature request issue though.