title: Javascript: How to add "div" element right after 2nd generic "p" tag (w/o ID nor Class) inside of every post or content section?
body: <p>How do I go about inserting a custom "div" element that appears right after 2nd generic (w/o adding ID or Class) "p" node/tag  in the content section of every pages I want it to be in, by using JavaScript?</p>
  
  <p>For example:</p>
  
  <pre><code>&lt;div id="main-content"&gt;
    &lt;p&gt;1st paragraph content.....&lt;/p&gt;
    &lt;p&gt;2nd paragraph content.....&lt;/p&gt;
    &lt;p&gt;3rd paragraph content.....&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>The output:</p>
  
  <pre><code>&lt;div id="main-content"&gt;
    &lt;p&gt;1st paragraph content.....&lt;/p&gt;
    &lt;p&gt;2nd paragraph content.....&lt;/p&gt;
    &lt;div id="custom-div"&gt;Content here...&lt;/div&gt;
    &lt;p&gt;3rd paragraph content.....&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>