Add cloud images page
This adds the cloud images page. It currently depends on the YAML manifest that we publish in the GitHub repo. Hopefully this is fine as a starting point. After the 3.13 release I'd like to migrate to doing a search using the AWS SDK and generating this on the fly with each site build.
In the next iteration of the page I'd like to add some Javascript search logic similar to the Ubuntu Cloud Image Locator but didn't have enough time to do that tonight.
To release 3.13 we'll just need to publish the images, update the YAML, and re-build the site.