Add question about Rust education materials

[apiraino]

Incorporating suggestion at Zulip link.

I think the other points in that Zulip message (w.r.t. to users desiderata) are now covered in #243 (possibly also other questions)

r? @Kobzol

[Kobzol]

This seems a bit ad hoc focused on courses. Are we not interested in more kinds of learning materials? E.g.:
What kind of learning materials have you tried? (select all that apply)

- Books (TRPL, Rust for Rustaceans, …)
- Online exercises (Rustlings, Rust by Example, ...)
- Videos
- Courses
- Something else (fill)

[apiraino]

fair point. I will reformulate the question+options

[Kobzol]

Looks good! I suggested "TRPL" as a shortcut, but probably in the final text we should spell it out fully, not everyone might be familiar with the shortcut.