Header font-weights previewed in edit mode

[tonilampela]

Describe your feature request

It would be nice if edit mode would already apply different font-weights for different level of headers.

# This line would have largest font
## This second largest
### This third largest

For illustration purposes of what I mean:

If header weights were previewed in edit mode it would be visually easier to work on a note / avoid mistakes with wrong header levels.

[gingerbeardman]

Agreed, it's one of the best things about Ulysses.

Obviously, should be an opt-in preference as it changes long-standing behaviour.