feature: merge tree and metadata panel

src/index.template.html

@@ -61,8 +61,8 @@
       },
       "panels": [
         {
-          "connector": [1],
-          "panel_label": "Contents",
+          "connector": [1, 2],
+          "panel_label": "Contents & Metadata",
           "show": true,
           "toggle": true
         },
@@ -77,12 +77,6 @@
           "panel_label": "Text",
           "show": true,
           "toggle": true
-        },
-        {
-          "connector": [2],
-          "panel_label": "Metadata",
-          "show": true,
-          "toggle": true
         }
       ],
       "rtl": false,