Doesn't work on MDX files

[RichardJECooke]

Describe the bug
LTex doesn't work on .mdx files, even after I ctrl-shift-p - activate ltex. Nor can I see any setting in the settings to enable it for .mdx. Can't see anything in the documentation either. I think this is a bug.

Steps to reproduce
Create an .mdx file. See LTex doesn't do anything.

Expected behavior
Ltex reports errors with squiggly lines.

LTeX configuration
Default new config when installing.

Version information
13.1.0

[RichardJECooke]

Workaround from https://stackoverflow.com/questions/65275709/how-to-see-preview-of-mdx-file-as-markdown-in-vscode

Set

"files.associations": {
"*.mdx": "markdown"
},