@drashna mentioned it'd be good to have a mention of the userspace in
the QMK structure section. Rather than rewrite the docs on userspace, I
chose to link to the existing documentation.
* Typo: Github => GitHub
* Typo: windows => Windows, docker => Docker, and some punctuations
* "QMK Introduction" links to the right file
* "Unix" rather than "UNIX", which is a trademark
* Directory name is "keyboards", not "keyboard"
* "handwired" is a subdirectory of "keyboards"
* Punctuation and minor fixes
* macOS rather than Mac
* Punctuation and other minor fixes
* Vagrant Guide links to an existing file
* Jun Wako referenced with his name rather than his nickname
* Saxon genitive 's outside the link