Massive mdbook update

updated instalation instructions for rusthello

fixed broken link to Enricos github

Fix "preparing the build" chapter linking back to a previous chapter as next step

Clear up the documentation for setting up and compiling

 - Update to latest mdbook
   - Switch to using book.toml
   - No empty links are allowed anymore. Comment out all empty links in
     SUMMARY.md
 - Add theme
   - Add favicon.png

Random updates

 - Update the asking questions page
 - Update the side projects page

Fix grammar in book.json.

Various updates and fixes

* Fix spelling: github -> GitHub, etc.
* Update the GitHub team list
* Move `null:` and `zero:` to the userspace schemes
* Change icons from Oxygen to Faba/Moka
* Remove statements that TFS is a ZFS implementation
* Add Intel HDA to the supported hardware
* Remove the `libredox` guideline
* Add some outgoing links where I think they're necessary

replace I with  we for consistency with rest of text

added cmake dependency

I didn't have cmake installed on arch, and my build failed. Thought it should be included in the book

Update outdated URLs

Since Bell Labs has died, the Plan9 project website only exists at a
mirror on 9p.io

add instructions for installing the toolchain

document the components of redox

Add punctuation, change wording

Change wording

"Null-terminated" is the more common term, and I think better suited to denote that the string (being the object) is being terminated by a null. Feel free to edit my commit in that regard, if you prefer the current ending.

"a URL…" being singular.

Fix typo