Add issue template for BUSL verification request

[rijkvanzanten]

As per the README, BUSL licenses have to be reviewed on a case by case basis:

fair.io/README.md

Lines 16 to 19 in 2eb2f80

	For **companies**, we are looking for a) a blog post announcement about b) a
	software product using a [Fair Source license](https://fair.io/licenses/). If
	you're using BUSL we will need to review your license more closely since BUSL
	can have highly variable implementations.

I think it'd be convenient to have another Issue Template for "BUSL License Verification Request" similar to the "Propose" templates