Remove node-unifi package dependency

- Add custom Unifi proxy built on existing cookie jar and httpProxy
- Change formatApiCall to emit empty string instead of undefined on missing key

src/widgets/unifi/widget.js

@@ -0,0 +1,14 @@
+import unifiProxyHandler from "./proxy";
+
+const widget = {
+  api: "{url}{prefix}/api/{endpoint}",
+  proxyHandler: unifiProxyHandler,
+
+  mappings: {
+    "stat/sites": {
+      endpoint: "stat/sites",
+    },
+  }
+};
+
+export default widget;