Short information about SW-Toolbox added.

Author: dumbNickname

index.html

@@ -942,6 +942,9 @@ <h1>And more ...</h1>
                 <p>
                     <a href="https://developers.google.com/web/fundamentals/instant-and-offline/offline-cookbook/" class="credits" target="_blank">Images from Jake Archibald`s offline cookbook</a>
                 </p>
+                <p>
+                    <a href="https://github.com/GoogleChrome/sw-toolbox" class="credits" target="_blank"><strong>SW Toolbox</strong> - no need to dive deep</a>
+                </p>
             </section>