Using strict equality in the JS example for City Quiz (#6373)

Co-authored-by: Nikhil Gupta <nikhil.gupta5667@gmai.com>

Author: jerrykodes

src/content/learn/reacting-to-input-with-state.md

@@ -84,7 +84,7 @@ function submitForm(answer) {
   // Pretend it's hitting the network.
   return new Promise((resolve, reject) => {
     setTimeout(() => {
-      if (answer.toLowerCase() == 'istanbul') {
+      if (answer.toLowerCase() === 'istanbul') {
         resolve();
       } else {
         reject(new Error('Good guess but a wrong answer. Try again!'));