Highlight edges between nodes that exceed belt capacity

[LucasPickering]

It'd be nice to be able to set current belt capacity (e.g. 270 for mk 3) and have the planner highlight any edges between nodes that exceed that throughput. For example, if you're making rotors and need 500 screws/min input, you can't fit it all on one belt. This would make it easy to tell which parts of the factory will require some extra consideration for belting. The current belt capacity would be configurable in the controls.

If this sounds like a good feature, I can give a shot at implementing it.