Restyle the Slides

## Do you have an eye for design?
Help us improve the look of the slide deck.
If you need help, check out the Appendix in the training manual.

Start by locating the slide deck and reading the Appendix in the training manual for guidance. Define the visual changes needed across the deck; done means the slides have a consistent, improved look.

索引モデルが issue の本文から書いたものです。