Fix mobile responsive design for footer

assets/css/default.css

@@ -290,7 +290,7 @@ input[type="search"]::-webkit-search-cancel-button {
   left: 0;
   right: 0;
   bottom: 0;
-  height: 30px;
+  max-height: 30vh;
 }
 
 body .footer a {

src/invidious/views/template.ecr

@@ -106,7 +106,7 @@
 
             <%= content %>
 
-            <div id="placeholder" style="margin: 8em;"></div>
+            <div id="placeholder" style="padding: 6em;"></div>
             <div class="footer">
                 <div class="pure-g">
                     <div class="pure-u-1 pure-u-md-1-3">