Small fix to example custom-server-typescript (#6695)

I noticed that the nodemon.json file was not watching for all file changes in the correct location for filetype .ts (typescript). After some research I found that the "ext" option in the nodemon.json fixes the issue and should work across all operating systems. 

examples/custom-server-typescript/nodemon.json

 {
-  "watch": ["server/**/*.ts"],
+  "watch": ["server"],
+  "ext": "ts",
   "exec": "ts-node --project tsconfig.server.json server/index.ts"
 }