Ignore mutations happens in nested Quill instance

(cherry picked from commit 8ce3ee3)

Header/paragraph doesn't reset list numbering in Firefox

(cherry picked from commit eeb976e)

(cherry picked from commit a6911aa)

- in chrome it take two left arrows to go to prev list item
- in firefox ctrl+left does not work

(cherry picked from commit 9d16aa5)

Without this a string with no space on a line will cause the break to
occur after the bullet but with it a string with spaces may not break at
the space. The latter is much more common and also the choice Paper
makes

(cherry picked from commit 232b6f4)

Fix checkbox not checkable on Firefox

(cherry picked from commit 1f0530a)