Fix Konami Code in Firefox with Quick Find

Fixes https://github.com/1j01/jspaint/issues/111

lib/konami.js

@@ -15,6 +15,15 @@ var Konami = {};
 			if (matchedKey) {
 				index += 1;
 
+				// fix for Firefox with "Search for text when you start typing" enabled
+				// https://support.mozilla.org/en-US/kb/search-contents-current-page-text-or-links
+				// prevent the default (opening Quick Search) for B and A,
+				// which are luckily at the end of the Konami Code sequence
+				// (otherwise it could prevent typing A and B in text fields unwantedly)
+				if (event.keyCode === 66 || event.keyCode === 65) {
+					event.preventDefault();
+				}
+
 				if (index === sequence.length) {
 
 					// reset when sequence completed