chore: convert to mime bundle for IPython reprs

[Henry Schreiner]

Let's convert _repr_svg_ (and any extras) to _repr_mimebundle_. See scikit-hep/decaylanguage#213.

[Henry Schreiner]

With this, we can also return nothing if the plot is too complex (I think), and that will revert to repr. I think. See #380

[Henry Schreiner]

Looks like we can return nothing with the html version too, so will use that.