Add new transformer for MDX v2

[Ayc0]

↪️ Pull Request

Other variant for #7922 to solve #7934.
The main differences are:

• we can have some custom config for MDX,
• pushed a new package @parcel/transformer-mdx-2 instead of modifying the existing.

For the MDX config, you can add a .mdxrc.js or .mdxrc.cjs file at the root of your repo to be able to customise MDX's behavior (see https://mdxjs.com/packages/mdx/#optionsremarkplugins).

Note: I tried to build parcel locally but yarn build-native gets stuck. So i couldn't test this PR locally

Note 2: to make it work, we also need @parcel/transformer-js as MDX v2 generates ESM code:

{
  "extends": "@parcel/config-default",
  "transformers": {
    "*.mdx": [ "parcel-transformer-mdx-2", "@parcel/transformer-js" ]
  }
}

💻 Examples

Previous MDX examples should still be applicable.

I also added a example here with some MDX config too: https://github.com/Ayc0/test-parcel/blob/7d05ca9/src/hello.mdx

🚨 Test instructions

Previous MDX tests should still be applicable.
But I also added a new one (not really sure if this is used).

I also created a repo here: https://github.com/Ayc0/test-parcel/blob/7d05ca9/src/hello.mdx

Notice the MDX 2 specific syntaxes like {a} or the MD in HTML, and that the strikethrough and the table work (provided by GFM):

Input	Config	Output

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[Ayc0]

On rebuild, parcel crashes with this error:

This might be a bug within Parcel: the import resolves the first time:

But after a recompilation, it crashes.

Edit: it only happens in parcel 2.8.0, in parcel 2.7.0 it works fine:

Screen.Recording.2022-11-13.at.01.32.57.mov

[devongovett]

That is caused by v8-compile-cache I believe...

[mischnic]

zertosh/v8-compile-cache#30

[Ayc0]

To follow https://github.com/mdx-js/mdx/blob/v1/packages/parcel-plugin-mdx/src/MDXAsset.js#L13, I could add mdx.config.js and mdx.config.cjs.

Or just use those 2 instead of .mdxrc.js (as usually the rc files are JSON files, not JS files)