initialize a sensor object: Explicitly require |options| to be a SensorOptions (#439)

This algorithm, invoked by the constructor of interfaces deriving from
`Sensor`, was accepting any dictionary. This meant it was possible, for
example, for any member (including `frequency`) to actually have any type
whatsoever.

Be more strict and require `options` to be a `SensorsOptions` instance, or
an instance of a dictionary inheriting from `SensorOptions`.

Author: Raphael Kubo da Costa

index.bs

@@ -1268,7 +1268,7 @@ to {{SensorErrorEventInit}}.
 
     : input
     :: |sensor_instance|, a {{Sensor}} object.
-    :: |options|, a [=dictionary=] object.
+    :: |options|, a {{SensorOptions}} dictionary instance.
     : output
     :: None