Fix assets and image location and references [Required for launch]

[SteveALee]

CC @shawna-slh

All static assets must be updated due to the limitations of Jekyll and the requirements to link to them in the integrated wai-website repo for publication.

What you need to do is:

• move assets to {projectroot}/content-assets/wai-aria-practices/ - eg see ACT rules assets
• Edit all assets references to be of the form `{{ @@@="/content-assets/wai-aria-practices/styles.css"}}

Likewise for the SVG files in 'content/assets' use {projectroot}/content-images/wai-aria-practices/ - you should rename the incorrect {projectroot}/content-images/wai-website-theme/

[SteveALee]

Oh I now see PR #9 which covers part of this.

[SteveALee]

Please move all images in /content-assets/wai-aria-practices to /content-images/wai-aria-practices

I know this is a bit messy but it's the convention we have for now.

If @shawna-slh agrees I propose leaving this to after the launch as it is mostly about source code structure.