Add MARP support to built-in slides viewer

Use case or problem

The built-in slides viewer is quite basic and doesn’t allow for any kind of custom visualization.

Proposed solution

MARP is a Markdown presentation framework that allows to add (limited) custom styling to Markdown slides. Would be great to support it in the official slides viewer.

Current workaround (optional)

A couple of community plugins add MARP support, but some are unmaintained. A native implementation would be better, in my opinion.