KaTeX with "mhchem extension"

[rsipakov]

Could you advise how can I set up the "mhchem extension", if possible do it? Also, can you please tell me why it is not possible to successfully update "remark-math" to version 4.0.0? Thank you!

[timlrx]

Try adding it to the document header? The current master branch relies on mdx/js which uses micromark 12. remark-math 4 is meant for micromark 13 libraries. The v1 branch of the code uses a newer xdm parser that supports remark-math ^4.0.0 and the package dependencies have already been updated to include that.