If you do `*` then space or `1. ` then space at the beginning of a line,
we automatically create a list. Now you can use undo to undo just the
automatic list creation, reverting to the plain text you typed.
On Chrome, if you made an inline formatting change, this would insert a
new <span> with a ZWS inside so we could focus it. Pressing Space would
remove this ZWS resulting in the focus ending up outside and so the
formatting would be lost. We were removing the ZWS so we could check
if we were at a block boundary correctly; instead, I've made it so the
boundary check can handle trailing or leading ZWS (see previous commit).
This is a massive refactor to port Squire to TypeScript, fix a bunch of small
bugs and modernise our tooling. The development was done on an internal
repository, so apologies to anyone following externally for the commit dump;
updates from here should come as real commits again.
Co-authored-by: Joe Woods <woods@fastmailteam.com>
