StateUtils: Use Array.prototype.findIndex instead of map => indexOf (#4106)

* Use Array.prototype.findIndex instead of map => indexOf

Creating a new array and iterating over all the routes is inefficient compared to findIndex, which does not create a new array and exits as soon as it finds a match. Since the indexOf method is used extensively this should provide a minor performance improvement

* reverted yarn.lock edits

src/StateUtils.js

@@ -21,7 +21,7 @@ const StateUtils = {
    * routes of the navigation state, or -1 if it is not present.
    */
   indexOf(state, key) {
-    return state.routes.map(route => route.key).indexOf(key);
+    return state.routes.findIndex(route => route.key === key);
   },
 
   /**