Add tooltips for suppressed chart values

[hangler]

If possible, add hover tooltips on charts for any 0, "S", "< 3", etc. data values

[hangler]

Do we want any part of the bar to appear?

If not, should hovering on the label trigger the tooltip, ideally?

[hangler]

We would want it upon hovering on the label, if feasible. Nice to have.