Fix #25 - React to Inspector.inspect events to enable the picker on iOS

It turns out we indeed need to enable/disable the Inspector domain before being able to listen to its events.
But on top of this, the response we get when the `inspect` event fires only contains a runtime object ID, which we need to translate into a node ID thanks to `DOM.requestNode`.
So it's going to be a little slower on iOS than on Chromium, but it should work.