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
* [x] OT support
* [x] Convert selected text to a list or selected list back to text
* [x] Add feature flags and session constraints
* [x] Default styles for numbered and bulleted lists

As this operation no longer *needs* to change as part of this PR, I'd suggest leaving this change out. OpSplitParagraph & OpInsertText should both be fixed as well for consistency... but this PR is already large enough without those.  :oncoming_bus: