Add MDX support

[thomaskoppelaar]

Adds MDX support.

MDX allows for JSX to be added into Markdown - I thought it would be great if this extension would allow that as well 😄

The syntax is the same as Markdown, the only thing that needs to be added is an extra switch case.

[theorlandog]

Would love to see this added

[voidranjer]

A temporary duct tape solution would be to add the following line to the VSCode settings.json:

{
  "pasteImage.insertPattern": "![${imageFileNameWithoutExt}](${imageFilePath})"
}

This hard codes it so that the CMD+OPTION+V shortcut works on all files regardless of the file extension (and yes, that includes .mdx too!)

More formatting options:
https://marketplace.visualstudio.com/items?itemName=mushan.vscode-paste-image