Some layers are missing from klayout/sky130.lyp

[urish]

The following fill layers are missing:

23/28 is fom.fill
28/28 is poly.fill
56/28   li1.fill
36/28   met1.fill
41/28   met2.fill
34/28   met3.fill
51/28   met4.fill
59/28   met5.fill

[mole99]

Hi @urish! I think this belongs in the sky130_klayout_pdk repo. There is already an open issue about the missing layers and I opened a PR to fix them, although I am not quite sure which naming is correct 🤔