Update README.md

Author: Kevin-Mattheus-Moerman

README.md

@@ -29,6 +29,7 @@ The optional input `numTypes` defines how many "things" or features are counted,
 * **Scroll**: Zoom in
 * **Delete key**: Changes to "delete mode"
 * **Backspace key**: Remove last added of current type
+* **Space bar**: Return to "counting mode" from "delete mode" 
 * **Number keys, e.g. 1, 2, 3, 4, 5, 6, 7, 8, 9**: Switch to counting this type
 * **Right arrow key**: Go to next image
 * **Left arrow key**: Go to previous image