Frontend: Put import map into its own file.

Change-Id: I0357d6961acedbae5b8ed8b65c45e7c8a5469178
diff --git a/src/main/resources/META-INF/resources/admin/index.html b/src/main/resources/META-INF/resources/admin/index.html
index 6e91fd4..d91bbdd 100644
--- a/src/main/resources/META-INF/resources/admin/index.html
+++ b/src/main/resources/META-INF/resources/admin/index.html
@@ -6,19 +6,7 @@
   <title>MulkCMS Admin</title>
 
   <script defer src="/node_modules/es-module-shims/dist/es-module-shims.js"></script>
-
-  <script type="importmap-shim">
-  {
-    "imports": {
-      "loose-envify": "/node_modules/loose-envify/loose-envify.js",
-      "js-tokens": "/node_modules/js-tokens/index.js",
-      "symbol-observable": "/node_modules/symbol-observable/es/index.js",
-      "redux": "/node_modules/redux/es/redux.mjs",
-      "lit-html": "/node_modules/lit-html/lit-html.js"
-    }
-  }
-  </script>
-
+  <script type="importmap-shim" src="/importmap.json"></script>
   <script type="module-shim" src="/admin/admin.js"></script>
 </head>
 
diff --git a/src/main/resources/META-INF/resources/importmap.json b/src/main/resources/META-INF/resources/importmap.json
new file mode 100644
index 0000000..42cae7b
--- /dev/null
+++ b/src/main/resources/META-INF/resources/importmap.json
@@ -0,0 +1,9 @@
+{
+  "imports": {
+    "loose-envify": "/node_modules/loose-envify/loose-envify.js",
+    "js-tokens": "/node_modules/js-tokens/index.js",
+    "symbol-observable": "/node_modules/symbol-observable/es/index.js",
+    "redux": "/node_modules/redux/es/redux.mjs",
+    "lit-html": "/node_modules/lit-html/lit-html.js"
+  }
+}