Keyboard shortcut to open folder on Windows

Based on Linux behaviour

keymaps/win32.cson

@@ -14,6 +14,7 @@
   'ctrl-alt-i': 'window:toggle-dev-tools'
   'ctrl-alt-p': 'window:run-package-specs'
   'ctrl-alt-s': 'application:run-all-specs'
+  'ctrl-shift-o': 'application:open-folder'
   'F11': 'window:toggle-full-screen'
 
   # Sublime Parity