docs: adapt contribution guide

frontend/.env.development-example

@@ -1,2 +1,3 @@
 # If the backend in your development environment is running on a different port, change the value of the variable below.
 DEVELOPMENT_BACKEND_URL=http://localhost:1411
+PORT=3000

frontend/vite.config.ts

@@ -16,6 +16,7 @@ export default defineConfig({
 	],
 
 	server: {
+		host: process.env.HOST,
 		proxy: {
 			'/api': {
 				target: process.env.DEVELOPMENT_BACKEND_URL || 'http://localhost:1411'