Makes note editing take up the full browser window

* Allows Google Keep editing to use the full browser window.
 * Allows toggling full screen on and off by clicking on an icon added on the notes.
 * Remembers full screen status across sessions
 * Supports Dark Mode
 * Works with non-English language settings
 * Options page to customize behavior (width, padding, background)
 * Customizable keyboard shortcut (Ctrl+Shift+F or Cmd+Shift+F by default) to toggle full screen on and off
 * Other minor bug fixes & enhancements

View Demo Here: https://cmp.onl/tjXo