add gfx.weather library & add weather.set command

src/logic/scripting/scripting_hud.cpp

@@ -36,6 +36,7 @@ void scripting::on_frontend_init(Hud* hud, WorldRenderer* renderer) {
     lua::openlib(L, "gfx", "blockwraps", blockwrapslib);
     lua::openlib(L, "gfx", "particles", particleslib);
     lua::openlib(L, "gfx", "text3d", text3dlib);
+    lua::openlib(L, "gfx", "weather", weatherlib);
 
     load_script("hud_classes.lua");