Allow to toggle the Web Inspector with keyboard shortcuts.

  This maps the keyboard shortcuts CTRL+SHIFT+I and F12 (these are
  standard ones as are used also on Chromium, Firefox and Safari).

  It keeps track also of whether the Inspector window is loaded or
  not, so the keyboard shortcut closes the inspector window when it
  is already loaded on a given tab.

https://bugzilla.gnome.org/show_bug.cgi?id=676870