Add pollution statistics to LuaForce

[Reika]

Basically lua access to the pollution tab of the statistics GUI, the way the other tabs have it (item production, fluid production, kills, etc).

[Rseding91]

That already exists: https://lua-api.factorio.com/latest/Lua ... statistics

[Reika]

That already exists: https://lua-api.factorio.com/latest/Lua ... statistics

OK, then a minor tweak to the docs page, to put it with its "siblings", would be a good idea.