Proposal: Increase headline margin for better readability

[puresick]

Hey there :wave:. First of all thank you for silverbullet. I am using it for a couple of weeks now and it is a blast!

One thing I noticed is the narrow spacing between headlines and paragraphs, which can make it hard to skim through long pages with lots of text including multiple headlines and paragraphs.

I would like to suggest adding a bit of margin to the top of headings. This gives them "a bit more room to breath" and results in a clearer distinction between sections on a page, e.g.:

I know about the possibility of custom styles, but this might be a general improvement for increasing readability. What do you think? I can also open a PR for this if there is interest in this change.