fix(docs): dead links (#507)

Author: jeertmans

docs/source/gallery.md

@@ -23,10 +23,10 @@ using Manim Slides presentations.
 
 Daniel publishes his presentations on *Cosmology, String Theory and related*
 topics on his
-[personal website](https://panopepino.github.io/Web_Page/main_page/slides.html). https://panopepino.github.io/Web_Page/main_page/slides.html
+[personal website](https://panopepino.github.io/web_page/main_page/slides.html). https://panopepino.github.io/web_page/main_page/slides.html
 
 For example, below are the slides of a seminar he gave titled
-[Our Universe on a (Dark) Bubble](https://panopepino.github.io/Web_Page/main_page/presentations/2023_11_long/LS.html).
+[Our Universe on a (Dark) Bubble](https://panopepino.github.io/web_page/main_page/presentations/2023_11_long/LS.html).
 
 <div style="position:relative;padding-bottom:56.25%;">
     <iframe
@@ -37,12 +37,12 @@ For example, below are the slides of a seminar he gave titled
         height="100%"
         allowfullscreen
         allow="autoplay"
-        src="https://panopepino.github.io/Web_Page/main_page/presentations/2023_11_long/LS.html">
+        src="https://panopepino.github.io/web_page/main_page/presentations/2023_11_long/LS.html">
     </iframe>
 </div>
 
 He also shares his code on a public
-[GitHub repository](https://github.com/PanoPepino/Manim_Theoretical).
+[GitHub repository](https://github.com/PanoPepino/mtheoretical).
 
 ### Jérome Eertmans