revert: remove custom issues.

We don't really need to have custom issues at all as they're either used incorrectly for bugs/requests, or seen asking general support questions which create communication issues between here and the support server. If someone wishes to bring up other things that do not feet the criterion of being a bugfix or feature request, they're more than welcome to talk about it in our **#stable**/**#unstable** development talk channels.

Author: i0bs