Scalar card axis clipped in Firefox

[stephanwlee]

Browser: Firefox 78 ESR.

As you can see on the screenshot, while the axis texts are rendered, the UI is currently clipped and is invisible even if you change the run selection (which was not the behavior in earlier version of Plottable + Chrome).

[stephanwlee]

Looks like the bug happened because the height on the label was larger than the container size (although the container's client rect seems big enough; it actually does this: ceil(16.13px + 5px) < floor(21.6px)`.

https://github.com/palantir/plottable/blob/cd8302fab3126c49b51ef60bde0da54765a9904b/src/axes/numericAxis.ts#L285-L288
https://github.com/palantir/plottable/blob/cd8302fab3126c49b51ef60bde0da54765a9904b/src/axes/axis.ts#L139-L161

By adding a margin, we can actually tell Plottable to allocate a little bit more height which will actually fix this issue.