MAPG-87 use HTML5 semantic elements, new styles, new footer

views/admin/map_editor.php

@@ -13,7 +13,7 @@ $jsFiles = [
 ];
 ?>
 <?php require ROOT . '/views/templates/main_header.php'; ?>
-<div class="header small">
+<header class="small">
     <h1>
         <a href="/maps" title="Back to playable maps">
             <img class="inline" width="1em" height="1em" src="<?= $_ENV['STATIC_ROOT'] ?>/img/icon.svg?rev=<?= REVISION ?>"><!--
@@ -47,7 +47,7 @@ $jsFiles = [
          --><span id="deleted" class="bold">0</span><!--
         --></span>
     </p>
-</div>
+</header>
 <div id="metadata" class="modal">
     <h2>Edit map data</h2>
     <form id="metadataForm" class="marginTop">