Toggle Native Tab Bar wót Irv66

While there are CSS solutions to hide the native tab bar while using a sidebar tab manager like Tree Style Tab or Sidebery, this addon focuses more on the ability to toggle the visibility of the tab bar when the user wants it. There may be times the user wants to see the sidebar, but need access to the native tabs for a short period of time.

Please follow the install instructions (Duplicated on Github here: https://github.com/irvinm/Toggle-Native-Tab-Bar) to enable userChrome.css usage and add a few lines to enable this solution.