Add info about NO_COLOR environment variable to readme

Author: kodie

README.md

@@ -514,6 +514,8 @@ Ahc\Cli\Output\Color::style('error', [
 Ahc\Cli\Output\Color::$enabled = false;
 ```
 
+Colors will be automatically disabled if the `NO_COLOR` environment variable is set to true.
+
 ### Cursor
 
 Move cursor around, erase line up or down, clear screen.