Lesson materials

[adamblanchard]

I propose we add a "materials" section to our lesson plans, so we can add slides, docs and other materials that mentors create as part of teaching the session.

Two reasons:

1. Share knowledge between mentors (especially new ones who join!)
2. Create a single, transparent place to store materials (instead of getting lost in team channels)

My idea is that they are shared here mostly for inspiration, but mentors could very well just use some previous materials instead of having to create their own.

Note: "Lessons" should now be called "Sessions" (source) but since that would trigger a lot of language updates in this whole repo I'm leaving it out for now.

[adamblanchard]

@rvedotrc Can we add your slides here too? Feel free to send them to me somewhere, and I can add to this PR.

I think it would be good to link to the source file, so future mentors could take yours and tweak it if they wish. If you did it on e.g. google slides, we could copy them to HYF drive so then you don't have to maintain the link staying alive yourself.

[rvedotrc]

@rvedotrc Can we add your slides here too? Feel free to send them to me somewhere, and I can add to this PR.

I think it would be good to link to the source file, so future mentors could take yours and tweak it if they wish. If you did it on e.g. google slides, we could copy them to HYF drive so then you don't have to maintain the link staying alive yourself.

I can, though I'm not ready to just yet, so please don't wait for me on this PR.