Reversion - Clickable wire labels

A [recent commit](https://github.com/AlgebraicJulia/Semagrams.jl/commit/afcf790f98dc746d1d65b308a46350f23ade3b8d#commitcomment-117121408) removed `pointerEvents` from the label text on a wire, so they can no longer be clicked on.

However, we would like to click on labels to interact with wires (e.g., rename).

Need to either
- add a handler for the text region (how to size it?)
- figure out a different way to ignore the labels during drag.