Ask Github to support mdx files

[ddickstein]

mdx isn't a good option for README files for Github projects because Github does not recognize the extension and render it with markdown. It would be great if the owners of this project could get in touch with the appropriate people at GitHub to add this support.

[mbarbin]

@ddickstein, I'm not a maintainer, just a user of ocaml-mdx but I have an input and a question.

• I have been using ocaml-mdx with files with extension .md and they are then recognized by GitHub.
• I didn't know about the .mdx extension. Is that a convention only, or does it enable more features?