Add guidance on timings and easing

[ci skip]

Detail when not to use easing

Add dropdown and hover examples

Add quick update animation

Update examples and labels to use sentence case.

Update copy.md  [ci skip]

Update copy.md [ci skip]

Update copy.md

Add new file for copy (messaging) guidelines

Update copy guidelines

Fix typo

Add forms to guidelines

Simplify Copy heading

Refine copy page. Add images and table

Fix toc link on Copy page