Consider increasing the space between list items to match viewer rendering

[laurent22]

See also: laurent22/joplin#11673

Normally list items are separated by larger margins than regular lines. In the Markdown editor however they are spaced like regular lines.

I'm not sure if it's technically possible but it would be good to set the margins so that they are the same as in the Markdown viewer (or RTE editor).

If it's easier to do this directly on the main repo it's fine too.