Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/tools/js/Shared/managers/ExtrasManagerContext.tsx

@@ -0,0 +1,21 @@
+import React, { useMemo } from "react";
+
+import { ExtrasManager } from "@dndbeyond/character-rules-engine/es";
+
+interface ExtrasManagerContextValue {
+  extrasManager: ExtrasManager;
+}
+const initContext: ExtrasManagerContextValue = {
+  extrasManager: new ExtrasManager(),
+};
+export const ExtrasManagerContext =
+  React.createContext<ExtrasManagerContextValue>(initContext);
+
+export function ExtrasManagerProvider({ children }) {
+  const extrasManager: ExtrasManager = useMemo(() => new ExtrasManager(), []);
+  return (
+    <ExtrasManagerContext.Provider value={{ extrasManager }}>
+      {children}
+    </ExtrasManagerContext.Provider>
+  );
+}