Animations in example gallery do not animate

[wtbarnes]

There is at least one example gallery entry that shows a resulting animation (https://docs.sunpy.org/projects/ndcube/en/latest/generated/gallery/creating_even_spaced_wavelength_visualisation.html#sphx-glr-generated-gallery-creating-even-spaced-wavelength-visualisation-py), but that animation is not actually animated in the rendered example gallery. To enable this, we should be setting the following config option in the sphinx gallery config as in sunpy,

https://github.com/sunpy/sunpy/blob/a986291976a7e250924197455f09630847706824/docs/conf.py#L28

[wtbarnes]

Ok, I need to take that back. It looks like that config option is already enabled and it appears to be down to the way the animation is being displayed. In the sunpy case, the things being displayed are matplotlib FuncAnimation objects. Maybe it is just a matter of returning that instead?