Allow opening multiple burndown panels

ext-src/getNonce.ts

@@ -0,0 +1,8 @@
+export default function getNonce() {
+  let text = "";
+  const possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+  for (let i = 0; i < 32; i++) {
+    text += possible.charAt(Math.floor(Math.random() * possible.length));
+  }
+  return text;
+}