add LICENSE

[Parikshit-Hooda]

This repo should have a license!
I would be happy to add one as part of hacktoberfest!

[mcpherrinm]

It does:
https://github.com/mozilla/Fira/blob/master/LICENSE

[binyamin]

@Parikshit-Hooda You might want to close this issue. (cc @potch)