Create FUNDING.yml

[nlopes]

Basically, I'm adding sponsorship here out of this discussion.

I'm adding two types:

• github sponsors: if you sponsor through this, I'll put this money towards charity (I'm fortunate enough to not need the money) or spend it all directly on this project (credits for CI, etc) depending on the project needs, but you have my guarantee I won't ever spend it on myself - I'm happy to do some transparent accounting if required.
• buymeacoffee: I'm adding this for very small donations - you should quite literally read it as "I'm going to have a coffee on your dime". If you don't like coffee or don't want me to have any personal gain out of your donation, don't use this one. If a company is sponsoring the project DO NOT USE THIS ONE