Remember that once your server is configured to see the public folder as the document root, no one can view the files that one level down that folder, which means that your .env file is already protected, as well your entire application. - That is the reason the public folder is there, security. - The only directories that you can see in your browser if you set the document root to the public folder is the folders that are there, like the styles and scripts.
You can make a test like this:
Enter in your project directory with the terminal and hit this:
php -t public -S 127.0.0.1:80
The -t means the document root, where the PHP built-in web server will interpreter as the document root. - see bellow:
-t <docroot> Specify document root <docroot> for built-in web server.
Now try to access the .env file, and you will see that you will get a 404 that the resource as not found.
Of course it's just an example, you will need to configure your sever to do the same.