feat: add distinct STORM weather type with wind-driven particles

Add Weather::Type::STORM enum value and wire it from SMSG_WEATHER type 3.
Storm particles are faster (70 units/s vs rain's 50), wind-angled at 15+
units lateral velocity with gusty turbulence, darker blue-grey tint, and
shorter lifetime. Previously storms rendered identically to rain.

include/rendering/weather.hpp

@@ -28,7 +28,8 @@ public:
     enum class Type {
         NONE,
         RAIN,
-        SNOW
+        SNOW,
+        STORM
     };
 
     Weather();