Better markdown support

[chrisui]

Plate has a handy plate-markdown package with a serialize + deserialize function however the serialize function does not have the same level of feature coverage as deserialize. Most notable tables but I imagine if table support is missing then several other features are.

A few q's:

1. Is this intentional?
2. Is anyone working on or is there a roadmap to improve coverage?
3. Has anyone encountered the same issue and has an alternative markdown pipeline?
4. Does it make sense to extend current implementation and open a PR back or does a contributor have an alternative plan/desire for this package?

My use case is storing documents in markdown and wanting to keep that while seamlessly deserialising from serialising to that format.

[felixfeng33]

table and math has already support in this pr will merge soon
#3998

[chrisui]

Great! If any extra testing or contribution is needed let me know. Happy to help to get over the line.

[felixfeng33]

we can pull their unit tests could you take a look?
you can commit to #3998 directly. let me know if you need permission

https://github.com/inokawa/remark-slate-transformer