Offsite link icons

[nutjob4life]

🤔 Tell Us About the Feature

NCI requires that public websites indicate links that lead away from the source domain be flagged with a special icon (and assistive annotations) so that users on government sites realize they're leaving a government site.

🎇 What Solution You'd Like

Something like in this screenshot from https://www.cancer.gov/about-cancer/coping/caregiver-support which has links to SignUpGenius and Lotsa Helping Hands:

〽️ Alternative Ideas

There ought to be a Plone add-on for this.

🗺 Context

Made a separate issue from #69

[nutjob4life]

Plone's lackluster implementation for this is up, but there are still some off-site icons that need manual highlighting.