Add "outDir": "./dist" to tsconfig.json (#853)

* Add "outDir": "./dist" to tsconfig.json

Add "outDir": "./dist" to tsconfig.json to fix "Cannot write file '.../astro.config.mjs" because it would overwrite input file.` error.

* Add comment for new option line

Co-authored-by: Chris Swithinbank <swithinbank@gmail.com>

src/pages/en/guides/typescript.md

@@ -29,7 +29,9 @@ Some TypeScript configuration options require special attention in Astro. Below
     // Enable stricter transpilation for better output.
     "isolatedModules": true,
     // Add type definitions for our Vite runtime.
-    "types": ["vite/client"]
+    "types": ["vite/client"],
+    // Tell TypeScript where your build output is
+    "outDir": "./dist"
   }
 }
 ```