Update displayOperands to handle optional operands

The displayOperands function previously did not distinguish between optional and required operands.
This change updates the function to display optional operands within square brackets.

Author: Linda-Njau

src/App.js

@@ -31,12 +31,19 @@ class App extends Component {
     displayOperands(operands) {
         let all = "";
         let comma = "";
+    
         for (let i = 0; i < operands.length; i++) {
-            all += comma + operands[i].name;
+            if (operands[i].optional) {
+                all += comma + "[," + operands[i].name + "]";
+            } else {
+                all += comma + operands[i].name;
+            }
             comma = ",";
         }
+    
         return all;
     }
+    
 
     displayMnemonic(item) {
         const spaces = "               ";