make switching tabs with key combinations possible

[graphql]

make switching tabs with key combinations possible

[timsuchanek]

CMD+ALT+LEFT_ARROW, CMD+ALT+RIGHT_ARROW, CMD+SHIFT+[, CMD+SHIFT+]

This probably needs to be added here https://github.com/graphcool/graphql-playground/blob/master/packages/graphql-playground-electron/src/main.ts#L54

It still can be explored if these combinations can be overriden in Chrome, but the main goal is to have them in the electron app.

In order to switch the tabs, something like this should be used in the ElectronApp.tsx as we want the state of the activeTab to live in the Playground.tsx component:

// ElectronApp.tsx
render() {
 return <Playground ref={ref => this.ref = ref} ... />
}

nextTab() {
  this.ref.nextTab()
  // in order to make this possible, Playground.tsx needs to expose a `public` method called nextTab
  // and prevTab, which the ElectronApp.tsx then can call
}