Add SPD extra videos (#1336)

Author: pulkitkrishna00

coursepages/spd/README.md

@@ -19,6 +19,7 @@ Alternative Links:
 - Work through Week 1A to Week 6A as given in the course overview. Watch the videos, do the exercises, and then solve the problems from the problem bank.
 - After you complete, Week 6A, do the [space invaders problem](https://github.com/ossu/spd-starters/blob/main/final/space-invaders-starter.rkt). You can find further instructions here: [Space Invaders Instructions](space-invaders-instructions.png). You can watch a sample run of the game [here](https://www.youtube.com/shorts/wUg3psZl7vM).
 - Then, work through Week 6B onwards. Watch the videos, do the exercises, and then solve the problems from the problem bank.
+- After that, watch the extra videos in [this playlist](https://www.youtube.com/playlist?list=PL6NenTZG6KrqdcyTwGf09uBxjI5pbXuT7).
 - After you complete all the modules in the course, do the [TA solver problem](https://github.com/ossu/spd-starters/blob/main/final/ta-solver-starter.rkt). You will find the instructions in the starter file.
 - The problem bank tab has many additional problems. We suggest you to solve all of them to boost your understanding.
 - Some links to starter files in the course are no longer working. You can download the starter files from this github repository: <https://github.com/ossu/spd-starters>. You can download a zip file of all the starter files using [this link](https://github.com/ossu/spd-starters/archive/refs/heads/main.zip).
@@ -43,6 +44,8 @@ Alternative Links:
 
 - If you are on Windows or Linux, use Alt + Backspace to delete whole words.
 
+- If you are unable to watch the videos on Edx for some reason, you can watch them on [this youtube channel](https://www.youtube.com/@systematicprogramdesign7962/playlists).
+
 ## FAQ
 
 ### This course is boring. Can I skip it?