odoc Add ability to call generate commands on asset units

The pipeline for asset was missing the generate command. This PR simply adds that!

The driver will need to be updated to follow the convention for installed asset described in https://github.com/ocaml/odoc/discussions/1113 (section: "Assets for installed packages").

Aug 01 '24 13:08 panglesd

(I'm not very proud of the name of the CLI option: --asset-path)

Aug 01 '24 13:08 panglesd

I have added support in the driver for the asset pipeline, following the convention.

This means, we now have images working for packages following the odig convention!

Aug 21 '24 08:08 panglesd

There's a broken asset in vg.lib.vg.Vg.P because it's using an hardcoded path but I couldn't make the reference syntax work. Asset references from libraries might not work.

Aug 21 '24 10:08 Julow

This has been rebased on top of #1188. html-generate and html-generate-asset have been split. The old asset pipeline has been removed: --child asset-... for compile and --asset for html-generate.

Aug 22 '24 15:08 panglesd

I think the driver is broken on main as it calls odoc html-generate-impl but I could test this a bit.

I'm being pragmatic and fixing this in this PR.

Aug 23 '24 10:08 panglesd