With Embroider, we can rely on async `import()` to do the splitting
for us.
This commit extracts from `pretty-text` all the parts that are
meant to be loaded async into a new `discourse-markdown-it` package
that is also a V2 addon (meaning that all files are presumed unused
until they are imported, aka "static").
Mostly I tried to keep the very discourse specific stuff (accessing
site settings and loading plugin features) inside discourse proper,
while the new package aims to have some resembalance of a general
purpose library, a MarkdownIt++ if you will. It is far from perfect
because of how all the "options" stuff work but I think it's a good
start for more refactorings (clearing up the interfaces) to happen
later.
With this, pretty-text and app/lib/text are mostly a kitchen sink
of loosely related text processing utilities.
After the refactor, a lot more code related to setting up the
engine are now loaded lazily, which should be a pretty nice win. I
also noticed that we are currently pulling in the `xss` library at
initial load to power the "sanitize" stuff, but I suspect with a
similar refactoring effort those usages can be removed too. (See
also #23790).
This PR does not attempt to fix the sanitize issue, but I think it
sets things up on the right trajectory for that to happen later.
Co-authored-by: David Taylor <david@taylorhq.com>
Generally follows the same pattern as #22520
There are some changes here, notably it uses the addon's babel
settings rather than the app's, and it goes through the same
treatment as the rest of the addon code (which may include more
than just babel).
However, this probably brings us closer to the normal expectations
you have around developing addon code, and in any case, does not
seem to have any effect on the final output:
```
$ diff dist/assets/markdown-it-bundle.js /tmp/dist-before/assets/markdown-it-bundle.js
```
