Allow reading camera zoom in LuaSimulation

[KikuGIe]

Pretty straightforward, in https://lua-api.factorio.com/latest/cla ... amera_zoom is write only, but if there's a need to track the zoom level, it can be assigned to a separate variable, since the default zoom is constant. However it adds extra complexity, so it would be easier to be able to read the zoom level as well.

[Koub]

[Koub] Moved to Modding interface requests