'Random Background Color Changer' docs: README.me add description step 4 (variation_2)

Author: AndriiKot

__4__step__/README.md

@@ -1,5 +1,25 @@
 <a id=top></a>
 
+<details>
+  <summary>
+    <h4>Description of the task</h4>
+  </summary>
+  <h3>Step 4</h3>
+  <p>
+      CamperBot is finished with building out the getRandomIndex function and it is working as expected.
+
+      But now they are running into this issue
+      when trying to create a reference to the
+      body element in the DOM:
+
+      Example Code
+      Uncaught TypeError: document.queryselector is not a function
+      A TypeError means that the code is trying to perform an operation on a value that is not of the expected type.
+
+      Fix the TypeError by updating the document.queryselector method to the correct method name that selects an element from the DOM.
+  </p>
+</details>
+
 # Random Background Color changer
 
 Debugging is the process of going through your code, finding any issues, and fixing them.