Added the documentation link of Jinja

Author: jhamukesh998

hello_app/templates/hello_there.html

@@ -9,3 +9,4 @@
         <span class="message">Hello there, {{ name }}!</span> It's {{ date.strftime("%A, %d %B, %Y at %X") }}.
     </body>
 </html>
+<!-- The above syntax makes use of jinja and it's documentation can be found over here http://jinja.pocoo.org/docs/2.10/templates/ -->