Update 'riesgos' layout

public/riesgos/index.html

@@ -39,11 +39,18 @@
                     </div>
                 </div>
             </div>
+            <div class="navbar navbar-expand flex-column flex-md-row bd-navbar">
+                <a href="../" aria-label="Regresar" class="navbar-brand text-dark">
+                    <i class="fas fa-arrow-left"></i>
+                    Regresar
+                </a>
+            </div>
         </div>
     </div>
 
     <div class="d-flex flex-column" id="mainContainer">
-        <header class="page-header py-2">
+        <header class="navbar navbar-expand navbar-dark flex-column flex-md-row bd-navbar">
+            <a class="navbar-brand mr-0 mr-md-2" href="." aria-label="Regresar"><i class="fas fa-arrow-left"></i></a>
             <div class="container text-center">
                 <div class="row align-items-center text-center" id="title">
                     <h2>Contenido de agua en la cuenca del r&iacute;o Grijalva</h2>