Easier access for people who would like to see the material

[blaa]

I occasionaly conduct various courses, today found reference to teach.rs and wanted to take a peek and see how it looks.

• I started with github repo, cloned it.
• I know the content is in files but it looked like it should be renderable to something.
• README points to modmod/README
• modmod has example command of building. But only partial? Only intro-track?
• It doesn't build with nightly in non-obvious way, had to change toolchain in rustup.
• It builds!
• Hm. What now.
• Ah, there's mdbook command and crutial path information on like 93 of modmod README after some directory listing.
• Should I use mdbook from Debian packages or from cargo? README points to Cargo. Seems to work with Debian package (which I already had, but I know nothing about mdbook)
• It works!

Suggestions:

• Later I found https://teach-rs.trifectatech.org/full/introduction.html that has the material - by googling. But it's not linked in README? It's not official?
• Maybe add some short example of all the commands required to render and start mdbook in the main README? Or a script?
• Maybe modmod could display mdbook command to display what you've just built?

Certainly it's doable now, just could be simpler for somebody with 15-30 minutes of time. ;)