Add upstream sources of yara signatures

[flamableconcrete]

Feature you would like to see: Ability to add upstream sources of yara signatures from popular repositories.

Why you need it: Other people write much better yara rules than me :)

How it should work: Unclear at this point. More of an idea I had while talking with a co-worker today. But if you could add a git repo as a source of yara files - and even better, if it could automatically update on a schedule - that would be awesome!

First repo that made me think of this idea:

• https://github.com/Neo23x0/signature-base

[flamableconcrete]

Oh, and it possibly could have gone without saying, but obviously there are a ton of other repos full of YARA rules found on the Awesome YARA GitHub page: https://github.com/InQuest/awesome-yara