Multiple sensor & sensor change discoverability

[rektide]

Hi.

In Background, we see some discussion of how multiple sensors are to be dealt with. I'm generally pretty ok with using SensorOptions passed to a sensor constructor to pick non-default sensors. There ought however be:

1. Some way to discover these sensors (such that my code can adapt to an 18 wheeler's worth of DirectTirePressureSensors automatically).
2. A way to detect sensors joining & leaving (for example, a gamepad with gyro being connected).

Some existing examples of specs tackling discoverability:

• Gamepad API enumerates gamepads with getGamepads() and exposes gamepadconnected and gamepaddisconnected events.
• Media Capture and Streams has an enumerateDevices() that returns a promise of all devices, and exposes a devicechange event signalling any change, with no payload.

There's good material here that could be replicated. Overall I'd prefer connected/disconnected events, since the sensor list could grow to be a very very considerable size and manually diffing that list to identify differences could be unpleasant.

Thank you all.

[rektide]

Closing as duplicate of #7.