Enable user-feedback and feature requests

[glooms]

Since we want to know what functionality our users feel is missing, it could be a good idea to make it easier for them to make feature requests.

One way to do this would be to suggest that they add features if they do something of the sort:

corectl variable

Perhaps with a message like this:

corectl has no command 'variable', do you think it should?
Feel free to make a feature request at https://github.com/qlik-oss/corectl/issues/new.

Another way would be to add a command that could be used for bug reporting or feature requests that opens corectl issues in a browser.