Add input rule for checkboxes

[juliushaertl]

• Allows to convert the current node checkboxes by typing "- [ ]"
• Fixes some positioning issues compared to regular lists

• Resolves: Enhance checkbox behavior #819
• Target version: master

Before:

After:

[juliushaertl]

This currently has the side effect that regular lists will only be converted after typing the first character after - , I'm not sure if there is an easy way around that yet.

[jancborchardt]

Great stuff, looks good design-wise! :)

[stefan-niedermann]

Nice! (Sorry, didn't check the code, but only the screen record)

• Does it also work if there is a space character between the brackets like - [ ]?
• Wouldn't it make more sense to replace the graphical checkbox when pressing backspack with the text representation - [ ] instead of removing it completely? At least for me this is the expexted behavior, but i don't insist to keep it, it's just well-known to me.

[juliushaertl]

• Does it also work if there is a space character between the brackets like - [ ]?

Yes, that is the case.

Wouldn't it make more sense to replace the graphical checkbox when pressing backspack with the text representation - [ ] instead of removing it completely? At least for me this is the expexted behavior, but i don't insist to keep it, it's just well-known to me.

Moved to #1307