feat: allow env variables to overwrite smtp config

Fixes #3

README.md

@@ -8,28 +8,30 @@ This is a simple logger for TypeScript projects with colors for console output.
 Logs are only printed if their log level is equal or higher than the defined log level.
 
 ## Log Levels
-Available Log levels are:
+Available log levels are:
 - 1 - INFO
 - 2 - LOG
 - 4 - WARN
 - 8 - ERROR
 - 16 - OK
 
-You can set your Log Level with the environment variable
-`STAPPS_LOG_LEVEL` in a binary way.
+You can set your log level with the environment variable `STAPPS_LOG_LEVEL`.
 
-For example `STAPPS_LOG_LEVEL=17` is 16 + 1 and would log everything
-that is `OK` or `ERROR`.
+To select your desired log levels add the corresponding numbers and set the value of `STAPPS_LOG_LEVEL` to the sum.
 
-If you want to use Logger in production (`NODE_ENV=production`) and allow all transports to fail set `ALLOW_NO_TRANSPORT` to `true`.
+For example `STAPPS_LOG_LEVEL=17` is 16 + 1 and would log everything that is `OK` or `INFO`.
+
+If you want to use logger in production (`NODE_ENV=production`) and allow all transports to fail set
+`ALLOW_NO_TRANSPORT` to `true`.
 
 ## SMTP
-This class also provides a simple implementation of an smtp transport which can be used as a
+This class also provides a simple implementation of an SMTP transport which can be used as a
 `TransportWithVerification` for the logger. You can use this to transport errors of the logger or to transport mails
 of your own monitoring solution.
 
 ### Usage
-You can instatiate it with a config or it will check for a config in the environment variables.
+You can instatiate it with a config or it will check for a config in the environment variables. Environment variables
+can overwrite the actual config values.
 
 Environment variables are:
 * SMTP_AUTH_USER:      SMTP username