Update README

Author: andreia

README.md

@@ -85,12 +85,14 @@ This package installs the [AWS SDK for PHP](https://github.com/aws/aws-sdk-php)
 
 You just have to add your S3 keys, region, and bucket using the following env vars in your `.env` file:
 
+```
 AWS_ACCESS_KEY_ID=
 AWS_SECRET_ACCESS_KEY=
 AWS_DEFAULT_REGION=
 AWS_BUCKET=
 AWS_URL="https://s3.amazonaws.com"
 AWS_POST_END_POINT="https://${AWS_BUCKET}.s3.amazonaws.com/"
+```
 
 To allow direct multipart uploads to your S3 bucket, you need to add some extra configuration on bucket's `CORS configuration`.
 On your AWS S3 console, select your bucket.