Changing time scales on interactions

[saulshanabrook]

Moving from heavyai/jupyterlab-heavyai#86

During our last call @niviksha mentioned that in immerse you can now zoom into a chart with a time scale on the x axis and it will rebin. This is similar to the desired behavior on geospatial charst, where if you zoom in, it should rebin at a finer granularity.

I mentioned this to @domoritz and he said this is currently not supported in Vega Lite and would be difficult to support because it would be hard to support in Vega. So one idea is to try to see if we could create a Vega chart that does this sort of auto-timescale binning. Part of the issue is that Vega doesn't support time units, so solving that issue would make this one easier as well: vega/vega#1310 (comment)

The intended behavior would be for the user to specify a "max bins" and it would choose the finest granularity, based on the current zoom state, going from years down to milliseconds.

[domoritz]

Vega now has time unit support so this should be doable.