Add guidance on timings and easing

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Detail when not to use easing

Add dropdown and hover examples

Add quick update animation

Describe hover, focus and active states for primary and secondary
buttons.

Organized the icons section in a table. Replaced images for icons
so they are all the same size.

Organized the color section in a table. Replaced the images with
new ones so the table would have a more manageable size. Updated
the values for some colors to show the $color-light shade.

Remove commented sections

Remove `db/schema.rb`

Add db/schema.rb from origin/master

Fix typos

Primary and secondary links should be dark blue on hover

Update anchor image to dark blue for secondary

Clean up markdown

Fix anchorlinks image

Fix spelling

Took it from https://gitlab.com/gitlab-com/www-gitlab-com/merge_requests/3232

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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

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