Prop: handsfree.id

This isn't really used yet but will be used to help distinguish between different instances of Handsfree. The id is always sequential, and the first instance always has an id of 1.

Example

const handsfreeA = new Handsfree({weboji: true})
const handsfreeB = new Handsfree({handpose: true})

// logs: 1
console.log(handsfreeA.id)

// logs: 2
console.log(handsfreeB.id)