[WIP] First cut at animating bar graphs

[rreusser]

This PR adds object constancy for bar graphs. It seems like barmode: 'relative' has problems.

barmode: 'stack':

barmode: 'group':

barmode: 'overlay':

barmode: 'relative':

[JonDum]

I'm sad this never landed! I just spent an hour trying to figure out why Bar charts weren't animating cause it seemed like such a simple thing that it must be supported.

[grahamscott]

I'm really interested to know if this is likely to land as a feature soon?

[rreusser]

@grahamscott I'm hoping will get a chance to loop back to it in the next week or so. Getting it started was pretty easy, but I don't yet know all the ins and outs of bar graphs and need maybe a day or two to lock down the remaining details. barmode: 'relative' is currently the one that was causing problems, though I suspect there are a decent number of details I still need to address.

[JonDum]

@rreusser I am 100% ok with some of the less commonly used bar modes not being supported at first if it means some form of support can be merged in the meantime.

[grahamscott]

@rreusser Thank you for getting back to me. I'm hoping we'll see this land then 👍