- Write the slides in markdown (bunige-demo.md), and convert it to a
  reveal.js presentation with pandoc (bunige-demo.html).
- Modifies the pandoc reveal.js template to improve the title slide.
- Ports the example slides of `index.html` to `bunige-demo.md`. There
  are still hickups with the structure.
- Updates the documentation accordingly, and explain how to modify the
  source files.

Co-Authored-by: iGor milhit <igor@milhit.ch>