Suptitle for show_rdms

[caiw]

Is your feature request related to a problem? Please describe.
When I'm writing a notebook, I like to add titles to all my plots. When I'm doing a quick show_rdms, I'd like to add a title to the figure, such as "Categorical model RDMs".

At the moment, if I run

fig, _axs, _items = show_rdm(model_rdms, rdm_descriptor="Name", pattern_descriptor="Conditions")
fig.suptitle("Categorical model RDMs")

I get:

This is probably because of the way tight_layout works?

Describe the solution you'd like
The figure returned by show_rdms to be amenable to adding a fig.suptitle(), so that the above code snippet instead produces something like:

This may be achievable by using constrained_layout instead of tight_layout, but I can't actually see where it's being set.

It might also be achievable by using pyplot.subplots_adjust(top=0.75) or similar (this fixes it for me in the above example), but the top arg should be determinable from the figure rather than guesswork.

Describe alternatives you've considered

• Just manually adjusting the output of show_rdms every time: the current situation.
• A dedicated title argument for show_rdms. However since it already returns the figure handle, and the figure has .suptitle(), that seems like the better way to do it, to avoid crowding the API.