Add support for datapacks retrieved from Modrinth

[itzg]

Assuming they’d be listed along with mods in MODRINTH_PROJECTS.

Didcussed in Discord

[itzg]

Dev note:

Datapacks still have a project type of mod; however, there is a "platform" (loader in the model) called "datapack".

[itzg]

Turns out this was a duplicate of #2126