chore: Setup dotenv for the express application

packages/backend/src/config/app-env.ts

@@ -0,0 +1,12 @@
+import * as dotenv from 'dotenv';
+dotenv.config();
+
+type AppEnv = {
+  port: string,
+}
+
+const appEnv: AppEnv = {
+  port: process.env.PORT || '3000',
+}
+
+export default appEnv;