Fix typo in import (#100)

switchbot/__init__.py

@@ -9,7 +9,7 @@ from .devices.bulb import SwitchbotBulb
 from .devices.ceiling_light import SwitchbotCeilingLight
 from .devices.curtain import SwitchbotCurtain
 from .devices.device import ColorMode, SwitchbotDevice
-from .devices.humidifer import SwitchbotHumidifier
+from .devices.humidifier import SwitchbotHumidifier
 from .devices.light_strip import SwitchbotLightStrip
 from .devices.plug import SwitchbotPlugMini
 from .discovery import GetSwitchbotDevices