Diagrams for CS126

[Justanhy]

Due to copyright concerns, we will no longer show diagrams of CS126 from the lecture slides.

As such, most of the diagrams in CS126 have been removed and now there is a placeholder instead.

While we intend to eventually do up our own diagrams, we would greatly appreciate voluntary pull requests. Diagrams in the pull request must

• Either be self-made, and by making a pull request you thereby grant us the permission to host it on this repo.
• Adhere to the licensing requirements as stated by the original author.

Thanks