First draft

This release contains the first draft of the SNN book. Some pieces are still missing -- more content will release as soon as it's ready.

New Contributors

• @Jegp made their first contribution in #3
• @pabogdan made their first contribution in #2
• @ggoupy made their first contribution in #39
• @cantordust made their first contribution in #94
• @eljoserass made their first contribution in #96

Full Changelog: https://github.com/open-neuromorphic/snn-book/commits/v0.8