Adds Missing syntax highlight to manual setup documentation (#298)

Author: yashug

docs/documentation/guides/manual.mdx

@@ -138,7 +138,7 @@ To establish an API route for interacting with Trigger.dev, follow these steps b
     1. Create a new file named `trigger.(ts/js)` within the `pages/api/` directory.
     2. Add the following code to `trigger.(ts/js)`:
 
-    ```
+    ```typescript
     import { createPagesRoute } from "@trigger.dev/nextjs";
     import { client } from "@/trigger";
     import "@/Jobs";