* Revise guide for generating reference docs
This PR changes the guidance for generating reference documentation for
Kubernetes API and kubernetes components. The topic of making changes to
the upstream repo is separated out because 1) it is not a mandatory step
for generating the reference docs; 2) it is about a more advanced level
of documentation fix.
* light copyedit
* more light copyedits
Karen Bradshaw
Jim Angel
Yang Li
Qiming