[Request] Allow modpack end-user to denylist certain files from being downloaded

[dimaguy]

I'd like to be able to deny certain files (like extra resource packs that aren't essential) from being downloaded every time I start the modpack.
This could be implemented by either an argument in the command line or a file in modpack directory

[comp500]

Note that the pack creator can mark files as optional (so the non-essential resource packs can be opt-in), see https://packwiz.infra.link/reference/pack-format/mod-toml/#option. In #6 I want to allow any file to be opted out of in the GUI, similarly to optional files. I think #13 would also apply to resource packs.