Add Window class and options plugin decoration

[ppot]

• Since the current: onWindow is the BrowserWindow and decorateBrowserOptions decorate it.
• Since the current onWindow doesn't refer to the Window object https://github.com/zeit/hyper/blob/canary/app/ui/window.js#L19
• Since Optimistic session creation #3352 Make session creation optimistic.

The current implementation make the session creation happen before the instance of the window. There for, if the plugin want to bind a session to a window. The new decorateSessionClass and decorateSessionOptions will result on the session not being accessible to the window's instance of the plugin. And therefor, not being able to bind it to an UID.

This PR include more extensibility by allowing the developer to either access onWindowClass the window's uid, or decorate it using decorateWindowClass.

This enable the possibility to give window's profile ID as unique name

exports.decorateWindowClass = defaults => {
  defaults = {uid: 'profileId_dev'};
  return defaults;
}

or acces the default UID created:

{ uid: 'b545deb5-c1e4-4ecd-af3b-e722126f1d40' }

Target: ppot/hyper-automator#4

[ppot]

@juancampa Review ;)

[juancampa]

Can we document this on https://github.com/zeit/hyper-site? @ppot at least open an issue with a short description 🙌

[ppot]

ya, will do tomorrow @juancampa ;)

[juancampa]

LGTM once we've added some documentation

[ppot]

PR made on the hyper-website ;)