Recompute column widths when the number of columns changes

[Kipre]

Recompute column widths on columns length change

I recently ran into an issue (when updating from beta 16 -> 41) where the tables would not behave the same way when presented with a dynamic number of columns. This is a proposal for making them behave like they used to, which in my opinion made more sense.

Current behavior

New (old) behavior

Notes

Didn't implement any tests yet, lmk if I should add a couple. The new entry in the demos is just for making it easier to test it in action, I don't think that it's a feature worth demonstrating.