Export functions for each phase

[devongovett]

Similar to #27 but with updated function names based on PR comments. In Parcel, we're looking to implement native support for MDX in Rust, and we'd like to avoid re-parsing since we already use SWC. See parcel-bundler/parcel#10064

Second commit may be more controversial. Basically I need a way to embed JSX expressions into Hast element nodes. In Parcel, we want to collect dependencies in MDX, e.g. image references and links. To do this, we need to transform <img src="foo.png" /> into <img src={new URL('foo.png', import.meta.url).toString()} />. The URL constructor creates a dependency in later stages.

I tried converting the Node::Element into a Node::MdxJsxElement in order to do this, but this gets treated as an "explicit" JSX element and no longer uses the injected _components.img. Simplest way to implement this was to add a JSX expression variant to PropertyValue but I could change it if there's a better way.

[wooorm]

Hi!

Why do that second part in hast, here, and not in swc when you get that later?
You already do things in swc land right?

It would probably be good to land mdx-js/mdx@e12f307 plus mdx-js/mdx@2c511a4 here.

Would be easier to split this PR up into 2? I’m 👍 on half, but not sure about changing hast like this

[devongovett]

Yeah I can do that. I had to split out mdx_plugin_recma_document and mdx_plugin_recma_jsx_rewrite as well so that my SWC pass can run before rewriting to use injected _components.