🧑‍💻(y-webrtc) use correctly the conf nodemon

The conf was not used correctly, the nodemon.json
was not used.
This commit fix this issue.

src/frontend/apps/y-webrtc-signaling/nodemon.json

@@ -1,5 +1,5 @@
 {
   "watch": ["src"],
   "ext": "ts",
-  "exec": "ts-node --esm ./src/server.ts"
+  "exec": "yarn build"
 }

src/frontend/apps/y-webrtc-signaling/package.json

@@ -7,7 +7,7 @@
   "type": "module",
   "scripts": {
     "build": "tsc -p .",
-    "dev": "nodemon --exec src/server.ts",
+    "dev": "nodemon --config nodemon.json",
     "start": "node ./dist/server.js",
     "lint": "eslint . --ext .ts"
   },