To-do

1. general styling
   • favicon
   • banner image below homepage title?
2. \mapsto -> \longmapsto in display mode (and similar for \to/\rightarrow)
3. some way of hiding/showing all videos on a page
4. explain gitbook buttons (in an html-only div)
5. only one footnote per paragraph
   • improve sidenote y-positioning using jquery
     • find the previous .footnote-ref in the DOM and align with that
6. pdf title page
   • include update date
7. embed youtube videos for lecture 8 (and 7?)
   • lite-youtube-embed
8. search for TO-DO and to-do
9. add more questions from problem sheets
10. TOC spacing in pdf (e.g. the §11.10 number overlaps with the subsection title)
11. {.tim} divs
12. $\rho^\mathcal{A}$ vs $\rho_\mathcal{A}$?