Add a flag to force a `ui.table` to follow the ticking part of a ticking table

[jnumainville]

Originally suggested by JJ in deephaven/deephaven-ipywidgets#48
This seems like something more appropriate to introduce in ui.table though.
Perhaps we could have an enum for a few different behaviors.

Some more ideas on top of what JJ suggested:
keep the scrollbar at the top (if the user hasn't scrolled):
starting_scroll="top"

keep the scrollbar at the bottom (if the user hasn't scrolled):
starting_scroll="bottom"

[mofojed]

In Grid, the props we use are isStickyBottom and isStuckToBottom to define whether it's possible to stick to the bottom of a ticking table, and whether it should be stuck to the bottom already. I think using those two should achieve what we're looking for.