Make the code could be formatted during rendering time

[quank123wip]

Please note that this is not a feature request, and I don't think it should be merged as a mainline plugin, as it's not a very common feature a markdown editor SHOULD have. Posting this just a way to ensure people who want this feature can see this.

As we can see, the code block is an important part in markdown syntax, besides we can let the markdown code have a good manner, the codes inside it should be formatted in some situations. However, this is a really complicated job. In fact, support all of them is impossible. I only have plan to support some languages fit in my need. Currently, I have plan to support JavaScript, Json, TypeScript(with Prettier) and C/C++(with wasm-bundled clang-format). It's definitely a very complicated job and this is an early idea for this. I don't have a roadmap or deadline for this.