Add styles for offsite links

[jmfee-usgs]

so users know before they leave the site.

[emartinez-usgs]

Any suggestions on what to do? I'm not sure there is a perfect convention that makes this obvious to the user. For example, some offsite icons look like some "open in new window" icons. Etc...

[lisa-usgs]

The icon you mention is what we have used previously on the legacy websites, and that would be fine.