Fix donations link

[fulldecent]

The donations link using Coinbase at the bottom of README.md is a broken link.

Also, please consider to add another option for donations using fiat. GitHub has a nice program for this. I'd like to send money your way from my company's open source fund. But I can't deal in Bitcoin.

[jessepollak]

I applied to Github Sponsors and will update this when I'm approved. Thanks!

[jessepollak]

P.S thanks for all your help on closing issues - if you're interested in being a co-maintainer, let me know! I try and do triage every couple months, but it's always less than I'd like..

[melloware]

@jessepollak I don't mind also being a triager or cleanup of old Issues tickets that are resolved etc?

[jessepollak]

Granted!