feat(enableKeyboardNavigate/lookup): keep buffer even in prefix match mode

This allow to change to buffer match if user typed a different
character later.

Author: marjune163

src/tpl/defaultTheme/frontend/index.js

@@ -376,8 +376,8 @@
 					// key changed, no more prefix match
 					lookupKey = '';
 				}
-				lookupBuffer += key;
 			}
+			lookupBuffer += key;
 			delayClearLookupContext();
 			return getMatchedFocusableSibling(container, isBackward, currentLookupStartA, lookupKey || lookupBuffer);
 		}