feat(developer): isRTL support for lexical model editor

Fixes #2556.

This adds support for `isRTL`, `insertAfterWord`, and
`quotesForKeepSuggestions` punctuation options for lexical models, both
in the parsing and in the user interface. A number of options are
presented to the user for the quotes and word breaking characters.

The parser continues to be a regex-based typescriptish parser. Expect it
to be gross. It's too big a job to do properly right now, so it is
somewhat limited and will bail if it finds structures it can't
understand.

I would hope to use something a bit smarter in the future to interface
with the editor. Probably when we are actually fully web-based and can
depend on a Typescript compiler directly.

Please don't get mad at me! 😟😟😟