* Overall cleanup for kubeadm setup guide.
* Add sonobuoy verification next step
* Partial copyedits
Hit a place where we also have formatting issues, plus a TODO (removed bc these changes go live as soon as merged). More work to do, but this should help the bottleneck for now.
* Address comments from reviewers
* Copy edits, fiddly bits, and clearer warnings
Incorporated feedback from @mistyhacks, fixed many nits, reorganized some **Note:** content more sensibly.
* Revised title per feedback
Liz