General accessibility issues

[downzer0]

In a meeting with @cptvitamin on 18 Jun we uncovered the following issues with accessibility for this Pattern Library site. We plan to address them.

• skip text in header, is in a heading; doesn't need to be
• use only a single skip link to the main content
• put the individual patterns in regions (which eliminates the second skip link)
• when scrolling, and focusing on the area, set focus right before the title
• convert individual patterns to regions; show up in the regions dialog box
• add SR text to Permalink so we know what they're for; don't make sense out of context
• on tab activation, focus should move to container.
• make tabs buttons
• aria-describedby not working on some fields, even though the markup is correct
• placeholder text, if it includes patterns or formatting, needs to be permanently on-screen (helper text is great)
• add a label to the size slider for icons
• range slider is aria-valuemax, aluemin, valuenow (misisng the value parts now)
• contrast issues with disabled buttons and inputs, lighter p text
• hover states blue on gray (gets lighter, so check the contrast)

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cc @talbs