Add ssltransport for robovacs (#943)

This PR implements a clear-text, token-based transport protocol seen on
RV30 Plus (#937).

- Client sends `{"username": "email@example.com", "password":
md5(password)}` and gets back a token in the response
- Rest of the communications are done with POST at `/app?token=<token>`

---------

Co-authored-by: Steven B. <51370195+sdb9696@users.noreply.github.com>

kasa/smart/smartdevice.py

@@ -802,6 +802,8 @@ class SmartDevice(Device):
             return DeviceType.Sensor
         if "ENERGY" in device_type:
             return DeviceType.Thermostat
+        if "ROBOVAC" in device_type:
+            return DeviceType.Vacuum
         _LOGGER.warning("Unknown device type, falling back to plug")
         return DeviceType.Plug