Add datepicker to timeline.

package.json

@@ -31,6 +31,7 @@
     "home-assistant-js-websocket": "^8.0.0",
     "keycharm": "^0.4.0",
     "lit": "^2.3.1",
+    "lit-flatpickr": "^0.4.0",
     "lodash-es": "^4.17.21",
     "moment": "^2.29.4",
     "propagating-hammerjs": "^2.0.1",