Prompt on close if unsaved/edited.

Would it be possible to add in a prompt on close, if the document is unsaved/edited to save at that point? 

Flow would be:
1. Edit saved Markdown document.
2. Do File Quit or Close the Window or Shortcut key to close program.
3. Prompt with Dialog that document is unsaved and closing would cause changes to be lost.
4. Offer Buttons to Save & Close, Close without Saving, Cancel( stop the exit and revert to the program)