Add separate edge font_size argument to mpl_draw

[rachtsingh]

I'm happy to implement this feature, just wanted to open an issue to make sure it's desired.

What is the expected enhancement?

Currently rustworkx.visualization.mpl_draw takes a single font_size argument which sets the font_size for both node and edge labels. Often, we want to shrink edge font sizes so that the edge is still visible (and the edge label isn't covered by the node), but with only one knob, it's difficult to get both right.

To avoid breaking existing code we could create an edge_font_size argument and default it to the font_size value, if set.

[mtreinish]

Thanks, I agree this is a useful feature, and for backwards compatibility I agree with your suggestion if no edge_font_size is specified that we default to the value of font_size used for nodes.