Extend hoverxref_roles

[Gallaecio]

@humitos suggested extending the hoverxref_roles setting of the corresponding Sphinx extension so that the display-on-hover behavior of the documentations works for things like signal or setting references.

[vinaykonuru]

I'd like to give this a shot.

[willbeaufoy]

@redrolor are you still working on this? If not I can take it.

[willbeaufoy]

As @redrolor didn't reply I have sent a pull request for this.