Create a 'download' language for fetching pre-built binaries

I'm aware of the requirement that additional dependencies for system hooks - the 'escape hatch' for hooks that don't fit into the python/node/go etc. managed environments list, such as shellcheck, must be installed outside of pre-commit in order to work.

Also aware of the python module that can be used to 'mirror' shellcheck in particular, though that feels a little hacky.

I'm sure you've given this thought before, and there's a very good reason why this hasn't been done, but, is it conceivable, with a PR I'd be willing to write, that additional dependencies could be supported for non-python etc. hooks?

I'm thinking along the lines of being able to specify a URL to a ZIP, which pre-commit would wget into its cache directory, storing a checksum so it could 'manage' when to re-download it, and then adding the directory to the front of $PATH when running the hook.

I'm sure it's not possible, but would be keen to know why, as there are a few hooks I use that this applies too and would feel like a useful addition for others.