content: open licenses in a separate browser tab
content: open licenses in a separate browser tab

Change-Id: I036ca9c27c6018c34806cfea0b8fbaefbd6baf33
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/606409
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite