mrm package is a dependency but is unused

[rdmurphy]

Unless I'm super missing something (always possible!) I don't see where the mrm package gets used anywhere.

rehype-prism/package.json

Line 33 in fb4174f

"mrm": "^3.0.9",

This is unfortunately the cause of some security issues being flagged on this library.

[russellpekala]

Seeing these as well. Tried to make PR but I don't think the security settings on this work for non mapbox people