Slack text snippet code highlighting

[oalders]

Slack supports Perl syntax highlighting in /snippet. This is possibly coming via CodeMirror. See https://slack.com/libs/webapp and https://github.com/codemirror/dev/

I got this via https://stackoverflow.com/questions/73235580/how-do-i-add-syntax-highlighting-in-slack-for-a-new-language

So, if there are syntax highlighting issues for Perl in Slack, that might be a good place to start.

[bmeneg]

Yesterday I noticed that GitLab snippets fails to recognize enclosing parenthesis during highlight (probably due to the colon before experimental):

And some time ago I noticed some failures in the middle of a pod doc:

GitHub seems to handle just fine both cases.

Reading the docs, it seems to be coming from highlight.js, which is distributed through the rouge Ruby gem.

[bmeneg]

I just opened a PR for adding the new class system support into highlight.js: highlightjs/highlight.js#3856