Add brightness to lightstrip's set_effect (#415)

* Add brightness parameter to lightstrip's set_effect

* Use None as default as effects have different default brightnesses

kasa/smartlightstrip.py

@@ -89,16 +89,19 @@ class SmartLightStrip(SmartBulb):
 
     @requires_update
     async def set_effect(
-        self,
-        effect: str,
+        self, effect: str, *, brightness: Optional[int] = None
     ) -> None:
         """Set an effect on the device.
 
         :param str effect: The effect to set
+        :param int brightness: The wanted brightness
         """
         if effect not in EFFECT_MAPPING_V1:
             raise SmartDeviceException(f"The effect {effect} is not a built in effect.")
-        await self.set_custom_effect(EFFECT_MAPPING_V1[effect])
+        effect_dict = EFFECT_MAPPING_V1[effect]
+        if brightness is not None:
+            effect_dict["brightness"] = brightness
+        await self.set_custom_effect(effect_dict)
 
     @requires_update
     async def set_custom_effect(