Code animation: Fixed layout integration

In experiment #155, I looked into making parts of the layout fixed. In this experiment, I will try to integrate it in 10 minutes

Update: It took 10 minutes. Also added a fly transition to the sidebar.

Snapshot

https://gitpod.io#snapshot/d77aa26e-ac00-4a5f-8d21-7b4d4f4ac25d

Demo

Notes

• fly transition for sidebar, should only run the first time the sidebar opens, and not when a secton selection is made.