.visible-xs(-block) => .hidden-sm-up

Fixes #17263.
[skip sauce]

I found non working anchors and some naming in consistency. I hope I fixed well. Have a nice day.

Fix #17177

Simplest example is using horizontal variants using rows.

Mostly links.
Fixes #17056.

Fix: #17145

Fix #17129

- Simpler main nav on all pages
- Back to purple masthead on homepage instead of dark graphite
- Active link styles on the main nav
- Cleaned up sidebar nav
- New docs layout name
- Homepage copy edits
- Updated bright purple docs color

- drop the index pages save for examples
- comment out the extend section for now
- fix up spacing fix on team list