* docs: Exceptions where pure white/black are allowed
* docs: Outline, style, fixes.
* Update rools/work README.
* Reorder and reword.
* Typo fixes.
* Distinguish between base and foreground colours
- They have very different usage patterns
- Gets us thinking about contrast and accessibility ;)
* Try to distil useful rules for base and fg colour selection:
- Former apparent black and white requirement as lightness limits
- Pure white is "widely accepted", or widely used at least
- Pure black is almost never used though (surprised me, but true)
* Add loads of example icons from Papirus itself.
* Mention "paper" shade as a suggested meterial colour
* Clarify margins and "design to" areas
* Document how shadows and highlights are made in detail.
* Remove language about a palette because there isn't any official one.
* Improve wording.
* Split out the design notes, fix main README links.
