Fixes#11628
PR #6389 caused bug #11628, which is a regression, as it had already
been fixed in #4441
It is likely that some things have changed because [Lexical had recently
made improvements](https://github.com/facebook/lexical/pull/7046) to
address selection normalization.
Although it wasn't necessary to resolve the issue, I added a
`NormalizeSelectionPlugin` to the editor, which makes selection handling
in the editor more robust.
I'm also adding a new collection to the Lexical test suite, intending it
to be used by default for most tests going forward. I've left an
explanatory comment on the dashboard.
___
Looking at #11628's video, it seems users also want to be able to
prevent the first paragraph from being empty. This makes sense to me, so
I think in another PR we could add a button at the top, just [like we
did at the bottom of the
editor](https://github.com/payloadcms/payload/pull/10530).
