Add ability to double-enter to create a new list item

[aurooba]

Right now the only way to add another list item is to either use the Add button in the list-item toolbar or use the block inserter. It would be seriously handy if you could just press Enter twice while in a list item, to add a new list item underneath and switch focus to the first paragraph in it to start typing.

[aurooba]

Related #6

[aurooba]

Upon some reflection, I'm not sure this is the right method. Using a an enter transform with maybe the characters >> might be more in line with what the Block Editor API already provides.

[cpryland]

Any keyboard-based method that isn't too convoluted would be better than nothing. But I still pine for double-return which makes the most sense, and which is a semi-standard in other editing systems.

[cpryland]

Oh, in fact, a double return is how the the normal List can be ended. (Not the same function, but same idea -- ending a list item and starting a new one.)