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Update outdated URLs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

Provide instuctions for people who just want to try Redox

fix chapter name in SUMMARY.md

The "Programs and Libraries" link in TOC doesn't work, this should fix it.

Add Programs and Libraries chapter (fixes #101)

I'm guessing, question marks indicate where I know I'm guessing.

Replaced the section named 'Compiling Your Program' with an up-to-date example

Fixes a few typos and makes some grammar changes.