Allow to pass integrity & async attribute to extra js

site/layouts/_default/examples.html

@@ -50,7 +50,9 @@
       {{ end }}
 
       {{ range .Page.Params.extra_js }}
-        <script src="{{ . }}"></script>
+        {{ $integrity := .integrity }}
+        {{ $async := .async }}
+        <script src="{{ .src }}"{{ with $integrity }} integrity="{{ $integrity }}"{{ end }}{{ with $async }} async{{ end }} crossorigin="anonymous"></script>
       {{- end }}
     {{ end }}
   </body>