fix(app.ls): chrome.experimental can be undefined

I did not turn on any experimental flags in `chrome://flags`, thus `chrome.experimental` is undefined on my machine.

The original `chrome.experimental.socket` throws an exception on my machine. The exception stops the execution of app.js and the socket never opens.

After changing to `chrome.experimental?socket` (and replace the extension ID to the ones on my machine) the extension worked like a charm.