📝 Mention environment variable option

README.md

@@ -30,18 +30,22 @@ After that `ackee-report` is ready to be used 🎉
 
 On the first run [ackee-report](https://github.com/BetaHuhn/ackee-report) will ask you to input a few values:
 
-- *ackee server* - the endpoint of your Ackee instance
-- *ackee token* - a permanent Ackee token (can be used instead of username and password, [more info](#ackee-api-authentication))
-- *ackee username* - your Ackee username ([more info](#ackee-api-authentication))
-- *ackee password* - your Ackee password ([more info](#ackee-api-authentication))
-- *email host* - the domain of the email server ([more info](#email-setup))
-- *email port* - the port of the email server ([more info](#email-setup))
-- *email username* - the username to use with the email server ([more info](#email-setup))
-- *email password* - the password to use with the email server ([more info](#email-setup))
-- *email from* - the from address to use ([more info](#email-setup))
+- *ackee server* / `ACKEE_SERVER` - the endpoint of your Ackee instance
+- *ackee token* / `ACKEE_TOKEN` - a permanent Ackee token (can be used instead of username and password, [more info](#ackee-api-authentication))
+- *ackee username* `ACKEE_USERNAME` - your Ackee username ([more info](#ackee-api-authentication))
+- *ackee password* `ACKEE_PASSWORD` - your Ackee password ([more info](#ackee-api-authentication))
+- *email host* / `EMAIL_HOST` - the domain of the email server ([more info](#email-setup))
+- *email port* / `EMAIL_PORT` - the port of the email server ([more info](#email-setup))
+- *email username* / `EMAIL_USERNAME` - the username to use with the email server ([more info](#email-setup))
+- *email password* / `EMAIL_PASSWORD` - the password to use with the email server ([more info](#email-setup))
+- *email from* / `EMAIL_FROM` - the from address to use ([more info](#email-setup))
 
 The configuration will be stored in your home directory under `~/.config/configstore/ackee-report.json` and can be changed at any point.
 
+### Environment Variables
+
+If you don't want to interact with [ackee-report](https://github.com/BetaHuhn/ackee-report) via the CLI interface, you can also specify each configuration option as an environment variable e.g. `ACKEE_TOKEN=<token>`
+
 ### Ackee API authentication
 
 [ackee-report](https://github.com/BetaHuhn/ackee-report) needs access to your Ackee instance via the API in order to get all the data it needs to generate the report. You can choose any of the two authentication methods below: