CST explorer?

I've spent the last few months working on a tool, [cst-tokens](https://github.com/js-cst-tokens/cst-tokens), that I believe will serve as a replacement for recast.

The idea of cst-tokens is to implement the basics of code transformation without any language or parser-specific logic. **This could give AST explorer the ability to allow users to easily write transforms for every single language it has a supported parser for!**

To do this each parser would need an associated cst-tokens grammar. This isn't as much of a problem as it sounds like because those grammars don't need define complete parsing logic. Instead a grammar just expresses (in essence) what the valid ways of printing a given AST might be. The cst-tokens engine can then use the grammar to recombine a given AST with its source text while tokenizing and attaching the tokens to the nodes they conceptually belong to. Because of the way the problem is simplified, a single grammar can be used to support every estree-compliant parser at the same time (including Babel which is only sort of compliant).

While all this is cool, it creates some architectural problems. cst-tokens isn't really a parser itself. It doesn't belong in the list of parsers. When it's active though, it needs to decorate/replace the tree that the active parser has generated. I don't know enough about how the AST explorer code is structured yet to understand what this would take to implement.