add support for lists

[masukomi]

this commit by @lucponnau shows a possible solution for supporting bullet lists but doesn't account for the fact that you can also make a bullet list with - (not just *) or that you can nest lists. Then there's the handling of <number>. lists (e.g. 1.)

We should

• be able to fold lists of all types
• be able to fold nested lists separately from their parents.