[Feature Request] PCB Editor: Add copper area info to board statistics

It would be nice to get per layer copper area info. Zones, tracks and pads combined with trough hole pads considered solid without a hole. Optionally as a percentage of board outline and free area (non copper).

This is manufacturing related info for e.g. electroplating or electrolytic etching. Naturally it provides optimization possibilities for reagent usage in chemical etching and immersion tinning with one off prototyping as well.