Document ENABLE_ESCAPES environment variable flag

Author: L0RD-ZER0

README.md

@@ -61,6 +61,7 @@ SLACK_ON_SUCCESS     | -                                                     | I
 SLACK_ON_FAILURE     | -                                                     | If set, will send the provided message instead of the default message when the passed status (through ``SLACK_COLOR``) is `failure`.
 SLACK_ON_CANCEL      | -                                                     | If set, will send the provided message instead of the default message when the passed status (through ``SLACK_COLOR``) is `cancelled`.
 SLACK_CUSTOM_PAYLOAD | -                                                     | If you want to send a custom payload to slack, you can pass it as a string to this variable. This will override all other variables and send the custom payload to slack. Example: `SLACK_CUSTOM_PAYLOAD: '{"text": "Hello, World!"}'`, Note: This payload should be in JSON format, and is not validated by the action.
+ENABLE_ESCAPES       | -                                                     | If set to `true`, will enable backslash escape sequences such as `\n`, `\t`, etc. in the message. Note: This only works for custom messages and not for the default message generated by the action.
 
 
 You can see the action block with all variables as below: