format of json list

template/slides/list.json

 [
-    {
-        "filename": "index.md",
-        "attr": {
-        }
-    },
-    {
-        "filename": "overview.md",
-        "attr": {
-        }
-    },
-    {
-        "filename": "thanks.md",
-        "attr": {
-
-        }
-    }
+    { "filename": "index.md" },
+    { "filename": "overview.md" },
+    { "filename": "thanks.md" }
 ]