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/config/index.ts

@@ -0,0 +1,16 @@
+/* eslint-disable no-process-env */
+/* global process */
+const environment = process.env.NODE_ENV;
+const debug = environment === "development";
+
+const config = {
+  buildKey:
+    typeof process.env.REACT_APP_BUILD_KEY === "undefined"
+      ? "UNKNOWN"
+      : process.env.REACT_APP_BUILD_KEY,
+  debug,
+  environment,
+  version: process.env.REACT_APP_VERSION,
+};
+
+export default config;