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/yet-another-abortcontroller-polyfill/index.js

@@ -0,0 +1,67 @@
+const root =
+  (typeof globalThis !== "undefined" && globalThis) ||
+  (typeof self !== "undefined" && self) ||
+  (typeof global !== "undefined" && global);
+
+if (typeof root.AbortController === "undefined") {
+  const SECRET = {};
+
+  root.AbortSignal = (function () {
+    function AbortSignal(secret) {
+      if (secret !== SECRET) {
+        throw new TypeError("Illegal constructor.");
+      }
+      EventTarget.call(this);
+      this._aborted = false;
+    }
+
+    AbortSignal.prototype = Object.create(EventTarget.prototype);
+    AbortSignal.prototype.constructor = AbortSignal;
+
+    Object.defineProperty(AbortSignal.prototype, "onabort", {
+      get: function () {
+        return this._onabort;
+      },
+      set: function (callback) {
+        const existing = this._onabort;
+        if (existing) {
+          this.removeEventListener("abort", existing);
+        }
+        this._onabort = callback;
+        this.addEventListener("abort", callback);
+      },
+    });
+
+    Object.defineProperty(AbortSignal.prototype, "aborted", {
+      get: function () {
+        return this._aborted;
+      },
+    });
+
+    return AbortSignal;
+  })();
+
+  root.AbortController = (function () {
+    function AbortController() {
+      this._signal = new AbortSignal(SECRET);
+    }
+
+    AbortController.prototype = Object.create(Object.prototype);
+
+    Object.defineProperty(AbortController.prototype, "signal", {
+      get: function () {
+        return this._signal;
+      },
+    });
+
+    AbortController.prototype.abort = function () {
+      const signal = this.signal;
+      if (!signal.aborted) {
+        signal._aborted = true;
+        signal.dispatchEvent(new Event("abort"));
+      }
+    };
+
+    return AbortController;
+  })();
+}