optimize submissions show page for mobile devices

app/views/icons/_chevron_left.html.erb

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" class="<%= local_assigns[:class] %>" width="44" height="44" viewBox="0 0 24 24" stroke-width="1.5" stroke="currentColor" fill="none" stroke-linecap="round" stroke-linejoin="round">
+  <path stroke="none" d="M0 0h24v24H0z" fill="none"/>
+  <path d="M15 6l-6 6l6 6" />
+</svg>