Merge #458: docs: [#457] update README file

7f68ea9 docs: [#457] update README file (Mario)

Pull request description:

  Resolves #457.

ACKs for top commit:
  josecelano:
    ACK 7f68ea9

Tree-SHA512: fd43a011d71388e20b021dc63de5faa5bcff6abedba51db2ef25997eff18df7c42d548a16b0e474b21378b92d8de84bd3b3f4b79ecfb30e21e655df736fbf161

Author: josecelano

README.md

@@ -67,6 +67,11 @@ git clone https://github.com/torrust/torrust-index-gui.git && cd torrust-index-g
 # Install dependencies
 npm install
 
+# Set up the .env file (if it doesn't exist, this is the normal behaviour with a newly cloned repo)
+if ! [ -f "./.env" ]; then
+    cp .env.local .env
+fi
+
 # Run development server
 npm run dev
 ```