express is runable

src/back/main.js

@@ -0,0 +1,14 @@
+const express = require('express');
+
+const app = express();
+
+app.use(express.json());
+
+app.get('/', (request, response) => {
+    response.status(200).send('elo fren!')
+})
+
+const PORT = 3003;
+app.listen(PORT, () => {
+  console.log(`Server running on port ${PORT}`);
+});