Support for code highlighting

[shonfeder]

Requested in https://github.com/ocaml/omd/issues/236#issuecomment-826293442. This should probably be implemented in a lightweight way that takes advantage of the clean extension mechanism we want (but don't yet have) ;)

[ghost]

There is a project called lowlight which integrates highlight.js with vdoms. It might be useful to do the same here where there is another project for integrating with jsoo vdom implementations.

[alan-j-hu]

Hi, I am using Omd to make a static site generator. One of the features I wanted for my static site generator was syntax highlighting, so I went and implemented it myself. I have published the textmate-language package for processing TextMate grammars on OPAM. I would love to work with the maintainers of Omd to integrate my existing work into Omd.

[sonologico]

Hi, @alan-j-hu, thanks! I'll take a look at your package to get an idea. As @shonfeder suggests, this might be a good opportunity to think about extensions more concretely.

[shonfeder]

I guess one place to start is with this question:

Is it (a) sufficient for our purposes that "extension" be through OCaml library APIs, or (b) do we need a plugin system that would allow different external executables to serve as extension mechanisms?

My current inclination is that (a) will suffice for current needs. The cost is that using a plugin means that you are either leveraging omd as a library, or you are building a new executable. Would this be satisfactory for your current needs @alan-j-hu?

If (a) is the right target for now, I propose we expore implementing it via a functorial interface. Later, we might consider adding something which is midway between (a) and (b) via ocaml_plugin (this would allow dynamically loading ocaml modules as plugins, but wouldn't work with arbitrary executables).

[alan-j-hu]

Yes, accessing the extension mechanism through the OCaml library should be sufficient for my needs.