add code text in html code example

Example: how to add text in html

<h1> This is h1 </h1> <!-- Biggest font-->
<h2> This is h2 </h2>
<h3> This is h3 </h3>
<h4> This is h4 </h4>
<h5> This is h5 </h5>
<h6> This is h6 </h6> <!--Smallest font-->