DEV: enforces link-rel-noopener linting rule (#8936)

* DEV: enforces link-rel-noopener linting rule

* oops

* better syntax

app/assets/javascripts/admin/templates/modal/admin-theme-item.hbs

@@ -2,7 +2,7 @@
   <div class="popular-theme-name">
     {{theme.name}}
     {{#if theme.preview}}
-      <a href="{{theme.preview}}" title="Preview" target="_blank">{{d-icon "far-eye"}}</a>
+      <a href="{{theme.preview}}" title="Preview" rel="noopener" target="_blank">{{d-icon "far-eye"}}</a>
     {{/if}}
   </div>
   <div class="popular-theme-buttons">