Update README.md

README.md

@@ -70,6 +70,7 @@ Options
 -c              : support classic lua version(5.1), default support 5.3
 -a              : attributes need to export, use ';' to separate, if ""-a"" only, all attributes whill be exported
 -e              : enums need to export, use ';' to separate, if ""-e"" only, all enums will be exported
+-ei             : enums is represented by a variable reference rather than a constant value, need to be used with -e
 -p              : do not use debug.setmetatable, in some Addon/Plugin environment debug object cannot be used
 -metadata       : export all metadata, use @CSharpLua.Metadata annotations for precise control
 -module         : the currently compiled assembly needs to be referenced, it's useful for multiple module compiled