Add disclaimer in main page

Change-Id: I2b7b5de09abdda059180f05ef6e3734c771f6954
diff --git a/index.php b/index.php
index 56a41fb..4f7dc8f 100644
--- a/index.php
+++ b/index.php
@@ -30,6 +30,8 @@
       </p>
     </form>
 
+    <p class="disclaimer">Font: <a href="https://developer.tmb.cat/">TMB</a>. Dades actualitzades cada setmana.</p>
+
     <script src="js/index.js"></script>
   </body>
 </html>