Teach config.go about the Riseup! Hidden Service

The current Riseup! hidden service is:

  ztmc4p37hvues222.onion

This .onion comes from the Riseup! chat documentation page:

  https://www.riseup.net/en/chat
Merge pull request #15 from ioerror/master

Add additional Hidden Service to config.go for Riseup! chat service