feature request: pager configuration for gps ls

[Alizter]

This is a bit of a niche request, but I think it would be nice to have a config option that pipes the output of gps ls into a pager.

When gps ls outputs a lot of things, sometimes its easier to read and cleaner to do gps ls | less. Having something like this as the configured behaviour would be nice.

[drewdeponte]

If we decided to support this. We should make sure that the pager configuration matches that of Git. That way we can properly use it to configure any of the commands that proxy to Git as well as use it to configure gps proper for commands that it owns.