General issues

[jtr13]

• [ ] change var to const or let as appropriate
• [ ] make all yScale domains fixed and remove code to update them
• [ ] improve consistency between lecture slides and text
• [ ] do not include data bind when defining inner plot group
• [ ] reduce dependencies between chunks run in the console, or add code as needed such as redefining svg
• [ ] clarify which code chunks should be run in the console