This switches to the new post composition logic in the post view. It
adds a space at the begging of a mention if it is needed.
We still need to make the state in these view more pure so we can test
more of the posting logic like cursor positions after posting, etc.
Changelog-Added: Add space when tagging users in posts if needed
Changelog-Fixed: Fix issue where typing cc@bob would produce brokenb ccnostr:bob mention
fe82134a75