Added script to create ".env" file

README.md

@@ -68,12 +68,17 @@ This application was proposed by [Juno](https://www.juno.com.br/), as part of th
 
 ## :hammer: Setting up the Environment
 
-To execute the application, you must have a Marvel Developer account and have the **public** and **private** keys generated. Once you have them, you will have to register both as environment variables in a `.env` file, at project root (use `.env.example` as reference to know all the required variables to be set).
+Make sure to have **Node.js 10+** installed in your machine and its **npm** available in the command line, then use the following command to install dependencies:
 
-Make sure to have **Node.js 10+** installed in your machine and its **npm** available in the command line, then use the following routines:
+```bash
+$ npm install
+```
+
+To execute the application, you must have a Marvel Developer account and have the **public** and **private** keys generated. Once you have them, you will have to register both as environment variables in a `.env` file, at project root. If it wasn't created after installation process, use `.env.example` as reference to know all the required variables to be set.
+
+At last, you can use the following commands to run the application:
 
 ```bash
-$ npm install     # Download dependencies
 $ npm start       # Run development server
 $ npm run build   # Build files for production
 ```

package.json

@@ -6,6 +6,7 @@
   "author": "Julio L. Muller",
   "homepage": "https://juliolmuller.github.io/marvel-characters",
   "scripts": {
+    "postinstall": "node -e \"require('fs').existsSync('.env') || require('fs').copyFileSync('.env.example', '.env')\"",
     "start": "react-app-rewired start",
     "build": "rm -rf docs/ && react-app-rewired build && mv build/ docs/",
     "test": "react-app-rewired test",