enhancementhelp wanted
Description
Just saw this GIF (from this post):

Currently MacDown allows cmd+] for indentation, but most editors (see TextEdit, Pages, MS Word, etc.) use tab for that purpose. Even I sometimes need to remind myself tab doesn’t work that way in MacDown.
AFAIK it doesn’t really make sense to insert tabs in the first line of a list item. But I’m not sure whether it’s just me. Please offer your thought on this, and if it does make sense I’ll start implementing it after the next release.