Added band str in 2D lecture video part 2

src/12_band_structures_in_higher_dimensions.md

@@ -18,10 +18,14 @@ _(based on chapter 16 of the book)_
     - examine 1D and 2D band structures and argue if you expect the corresponding material to be an insulator/semiconductor or a conductor.
     - describe how the light absorption spectrum of a material relates to its band structure.
 
-??? info "Lecture video"
+??? info "Lecture video (part 1 of 2)"
 
     <iframe width="100%" height="315" src="https://www.youtube-nocookie.com/embed/eTx8FnVQ0pw" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
 
+??? info "Lecture video (part 2 of 2)"
+
+    <iframe width="100%" height="315" src="https://www.youtube-nocookie.com/embed/Or50p4-HRiA" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>
+
 ## Band structure
 
 How are material properties related to the band structure?