Stage width/height is set after monitors loaded, supposedly breaks them

[GarboMuffin]

[SharkPool-SP]

*breaks positioning to be exact

[SharkPool-SP]

Push these commits:
runtime.js:
PenguinMod@df2d440

sb3.js
https://github.com/PenguinMod/PenguinMod-Vm/blob/develop/src/serialization/sb3.js#L1713-L1731