Add archived document box

[yatil]

And then add to https://github.com/w3c/wai-wcag-mob-overlap and https://github.com/w3c/wai-shared-experiences

[yatil]

@slhenry Can you please give feedback on the implementation here: https://w3c.github.io/wai-website-components/components/preview/archived.html

(I tried using red first and while it looked great, it was too daunting, so I switched to yellow.)

[yatil]

• [x] Make text editable between documents
• [x] Add verbiage to the title
• [x] Create template hooks
• [x] Use “archived” instead of “retired”

[yatil]

Done from a design/theme perspective.

[yatil]

Re-Open because of the comments in #136 and https://github.com/w3c/wai-shared-experiences/issues/2.