Add script to download Fabric mods automatically

[iminlikewithyou]

https://docs.modrinth.com/api-spec

Windows - %appdata%.minecraft
macOS - ~/Library/Application Support/minecraft
Linux - ~/.minecraft

we don't know what client they're using so the best bet is to download the mods to an output directory and have the user manually drag the files in after opening the (possible) mods directory in their respective .minecraft folder

i contend this is worse than just adding proper support for good clients (like MultiMC)