Code highlighting for raku

I'd love to be able to see raku code embedded in a markdown text. I've got a minimal `prism-raku.js`, dumped that into `vendor/prism/` of the unzipped xpi, zipped the directory as `markdown2.xpi`, uninstalled the original version and installed mine (using `about:debugging`) in firefox, but my raku code remained black. What am I doing wrong? Is somebody already working on that?