Add noopener and noreferrer to new window links
Add noopener and noreferrer to new window links

Fixes #1095

We're using [target=_blank] which has a vulnerability
https://mathiasbynens.github.io/rel-noopener/

“To prevent pages from abusing window.opener, use rel=noopener. This
ensures window.opener is null in Chrome 49 and Opera 36.”

“For older browsers, you could use rel=noreferrer which also disables
the Referer HTTP header”

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