Add YouTube video link for manim

Added a link to a YouTube video about Manim.

Author: StevenClontz

source/ch-manim.ptx

@@ -366,6 +366,13 @@ This chapter is co-authored by <xref ref="frontmatter">Tien Chih</xref>.
                                 a Discord for Manim, people can help here and you can run Python code within the Discord.
                             </p>
                         </li>
+                    
+                        <li>
+                            <p>
+                                <url href="https://www.youtube.com/watch?v=UzEoWUGstVU">https://www.youtube.com/watch?v=UzEoWUGstVU</url>
+                                an excellent video by Bismuth, using Manim and the framework of Super Mario speedrunning to communicate mathematics.
+                            </p>
+                        </li>
                     </ul>
                 </p>
             </statement>