Show every message under its own heading

[lukemt]

Make it possible to configure role::user|assistant to be headings e.g. ## role::user

Setting the setting to 0 deactivates the functionality.

I set heading level 2 as default here, but you can change it to 0 if you don't like it as default.

[lukemt]

example before:

example after:

[bramses]

looks good! I'll change the default to 0 as to not disrupt anyone's current workflow then I'll merge it in. Thanks for the PR @lukemt!

[lukemt]

Makes sense. Awesome!