Add shortcuts

- Removed unnecessary IIFE. 
  - Gets rid of the unused `init` assignment.

- Added in undo/redo keyboard shortcuts. …
  - Adds in keymaster by @madrobby to handle shortcuts.
  - Introduced a method that will ensure an element is enabled before
    triggering a click, used for filtering undo/redo eligibility.
  - Added keybinding aliases ctrl+z/ctrl+y for undo/redo.