Add JSONfn as dependency and use it to parse chartjs options

This enables functions to be passed as options, e.g. for custom formatting of scale/axis tickmarks:
{...

"scales": {
"yAxes":{
"ticks": {
"callback": "function(value){return value+'%' }"
}
}
}
...
}

package.json

@@ -49,7 +49,8 @@
     "prettier": "^2.3.0",
     "sort-package-json": "^1.50.0",
     "vuepress": "^1.8.2",
-    "vuepress-theme-gungnir": "^0.2.0"
+    "vuepress-theme-gungnir": "^0.2.0",
+    "json-fn": "^1.1.1"
   },
   "useWorkspaces": true
 }

packages/plugins/chart/lib/Chart.vue

@@ -6,6 +6,7 @@
 
 <script>
 import Chart from "chart.js";
+import JSONfn from "json-fn";
 
 export default {
   name: "Chart",
@@ -20,7 +21,7 @@ export default {
     }
   },
   mounted() {
-    const data = JSON.parse(this.code);
+    const data = JSONfn.parse(this.code);
     const ctx = this.$refs.chartjs.getContext("2d");
     new Chart(ctx, data);
   }