startContainer is not necessarily a sibling to endContainer at this
point. endContainer is definitely at the right level of the hierarchy
so instead just get the previous sibling from this and merge with that
if it's also a text node.
We merge a faux block with contents from after a split point when
inserting HTML. The merge function presumes this block has already had
fixCursor run on it to ensure we add the <br>s some browsers need to
support correct cursor focusing.
Fixes#451
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>
