Validate resource pack URLs and zip files

[Phoenix616]

Is your feature request related to a problem? Please describe.

Some hosts (like mediafire, google drive, etc) will not work properly when used as pack urls which leads to errors.

Describe the solution you'd like

Validate the URL as well as that the zip has a proper resource pack setup and is not some other pack type.

Describe alternatives you've considered

A wiki page explaining the differences. Would need to be repeated to users every time though.

Additional context

The zip file check will detect non-direct download links too so that doesn't really need to be split in two. Temporary links can't really be detected so some blacklist for mediafire&co should be included.