Grabbed dndbeyond's source code

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

ddb_main/node_modules/tss-react/tools/assert.js

@@ -0,0 +1,11 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.assert = void 0;
+/** https://docs.tsafe.dev/assert */
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function assert(condition, msg) {
+    if (!condition) {
+        throw new Error(msg);
+    }
+}
+exports.assert = assert;