Add Mods Checker

[Bwc9876]

Adds a new action that checks newly added mods for some basic sanity:

• Checks if the mod's repo is available
• Checks if there's a release with an asset
• Checks if the unique names, versions, etc match
• Warns on no description or non-semver versioning
• Checks if the unique name of a mod is alredy in-use
• Checks if the manifest points to a non-existent DLL file
• Checks if the dependencies listed in dependencies actually exist in our database

This is somewhat tested, but idk how well it'll work