[enh] simple theme: mobile layout: allow access to the preferences

when there is no query, reduce the width of the query field,
to display the preference button on the right.

searx/static/themes/simple/src/less/search.less

@@ -195,6 +195,11 @@
     flex: 1;
   }
 
+  #main_results #q:placeholder-shown ~ #send_search {
+    margin-right: 2.6rem;
+    transition: margin-right 0.1s;
+  }
+
   .search_filters {
     display: block;
     margin: 0.8em 0;

searx/static/themes/simple/src/less/style.less

@@ -724,10 +724,13 @@ article[data-vim-selected].category-social {
   }
 
   #linkto_preferences {
-    display: none;
-    position: fixed !important;
-    top: 100px;
-    right: 0;
+    top: 0.8rem;
+    right: 0.7rem;
+  }
+
+  #main_index #linkto_preferences {
+    top: 0.5rem;
+    right: 0.5rem;
   }
 
   #results {