internal/frontend: copy import statement
internal/frontend: copy import statement

The copy button at the top of a details page now puts

   import "path"

on the clipboard, rather than just path. This makes
it easier to simply paste the result into Go code.

Fixes golang/go#36809.

Change-Id: I52360a3d1a02214b10a27d39f9d0b2ddad7e0d4e
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/665367
CI-Result: Cloud Build <ea5729d4cf3392b9d382b6ca272c65aa27554f44@system.gserviceaccount.com>
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>

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