fix: correct onError middleware syntax in docs (#2537)

* fix: correct onError middleware syntax in docs

Fixes #2517

Removed nested onError function that caused TypeScript error.
The correct syntax is to directly return an Error instance from
the onError method, not nest another onError function inside it.

* chore: add changeset for middleware onError docs fix

Author: lindseystead

.changeset/fix-middleware-onerror-docs.md

@@ -0,0 +1,7 @@
+---
+"openapi-fetch": patch
+---
+
+Fix incorrect `onError` middleware docs example that caused a TypeScript error when copy-pasted.
+
+

docs/openapi-fetch/api.md

@@ -242,9 +242,7 @@ const myMiddleware: Middleware = {
   },
   async onError({ error }) {
     // wrap errors thrown by fetch
-    onError({ error }) {
-      return new Error("Oops, fetch failed", { cause: error });
-    },
+    return new Error("Oops, fetch failed", { cause: error });
   },
 };
 

docs/openapi-fetch/middleware-auth.md

@@ -29,9 +29,7 @@ const myMiddleware: Middleware = {
   },
   async onError({ error }) {
     // wrap errors thrown by fetch
-    onError({ error }) {
-      return new Error("Oops, fetch failed", { cause: error });
-    },
+    return new Error("Oops, fetch failed", { cause: error });
   },
 };