docs: fix bun, cf workers, and nodejs import paths for index.ts (#859)

Author: NathanFlurry

docs/platforms/bun.mdx

@@ -30,7 +30,7 @@ Bun provides a fast runtime environment for running ActorCore, with excellent pe
 
     ```typescript src/index.ts
     import { serve } from "@actor-core/bun";
-    import { app } from "./app";
+    import { app } from "../actors/app";
 
     // Start the server with file-system driver (default)
     serve(app);

docs/platforms/cloudflare-workers.mdx

@@ -51,7 +51,7 @@ The Cloudflare Workers platform with Durable Objects provides a robust environme
 
     ```typescript src/index.ts
     import { createHandler } from "@actor-core/cloudflare-workers";
-    import { app } from "./app";
+    import { app } from "../actors/app";
 
     // Create handlers for Cloudflare Workers
     const { handler, ActorHandler } = createHandler(app);

docs/platforms/nodejs.mdx

@@ -44,7 +44,7 @@ Node.js provides a robust environment for running ActorCore, ideal for developme
 
     ```typescript src/index.ts
     import { serve } from "@actor-core/nodejs";
-    import { app } from "./app";
+    import { app } from "../actors/app";
 
     // Start the server with file-system driver (default)
     serve(app);