Fix elements list URL

Currently in useful links people are directed to elements.nuxeo.com
As mentioned in SUPINT-689 we'd like to change that URL to https://www.webcomponents.org/author/nuxeo

TODO

• Check if we prefer to keep elements.nuxeo.com (allows us to change the redirect in case we want to change URL in the future) or provide a direct link to the currently wanted page
• Adapt code accordingly if needed