Add appendix section: classroom facilitation tips

While this guide is awesome, let's make it even easier for the trainers to be 💪!

I'd like to have a section on facilitation/general teacher tips:

- [ ] Suggestions for keeping the class on track (i.e. time management techniques)
- [ ] Setting up logistics in the beginning (e.g. in the event students are training at a building/site they aren't typically at, where does stuff like the bathroom and 🍕 exist?)
- [ ] Have a method to capture off topic ideas/questions (e.g. parking lot)
- [ ] Techniques for keeping the class engaged when they take a moment to visit ☁️ ☁️ ☁️
- [ ] Links out to resources (let's not recreate the wheel)

I'm sure there's more that I'll think of as going through this. Feel free to make suggestions!