move three.js importmap to a specific include

_includes/three-imports.html

@@ -0,0 +1,8 @@
+<script type="importmap">
+{
+  "imports": {
+    "three": "/vendor/three/r170/build/three.module.js",
+    "three/addons/": "/vendor/three/r170/examples/jsm/"
+  }
+}
+</script>

_layouts/default.html

@@ -1,5 +1,6 @@
 <!DOCTYPE html>
   <head>
+    {% include three-imports.html %}
     {% include head.html %}
   </head>
 <body>
@@ -16,13 +17,6 @@ <h1 class="display-5" data-i18n="home.master">
         <idf-viewer id="building" src="/models/example.idf" style="height: 500px"></idf-viewer>
       </div>
   </main>
-  <script type="importmap">
-  {
-    "imports": {
-        "three": "/vendor/three/r170/build/three.module.js",
-        "three/addons/": "/vendor/three/r170/examples/jsm/"
-    }
-  }
   </script>
   <script type="module" src="/lib/modules/components/idf-viewer.js"></script>
   <script type="module" src="/lib/modules/components/idf-legend.js"></script>