[Draft] Create numbered and bulleted lists

This PR aims to add the creation of lists in a document. This only aims to support numbered and bulleted lists and not image bullet lists for now.

# TODO
* [x] Editor UI buttons
* [x] Detect list style at selection
* [x] Ops for list insertion/removal
* [ ] OT support
* [ ] Convert selected text to a list or selected list back to text
* [ ] Default styles for numbered and bulleted lists

This was actually incorrect behaviour (e.g. didnt work for a list starting at 1.1) so it has been changed but there is still an assertion that the position supplied to the op is the first step in the list.