feat: add empty annotation panel

src/index.template.html

@@ -77,6 +77,12 @@
           "panel_label": "Text",
           "show": true,
           "toggle": true
+        },
+        {
+          "connector": [5],
+          "panel_label": "Annotations",
+          "show": true,
+          "toggle": true
         }
       ],
       "rtl": false,