Update usage

README.md

@@ -50,7 +50,7 @@ For command line use, choose your preferred installation:
 ```
 Usage: xscgen [OPTIONS]+ xsdFile...
 Generate C# classes from XML Schema files.
-Version 2.0.522.0
+Version 2.0.792.0
 xsdFiles may contain globs, e.g. "content\{schema,xsd}\**\*.xsd", and URLs.
 Append - to option to disable it, e.g. --interface-.
 
@@ -162,6 +162,7 @@ Options:
  --ar, --useArrayItemAttribute
  use ArrayItemAttribute for sequences with single
  elements (default is true)
+ --es, --enumAsString Use string instead of enum for enumeration
  --ca, --commandArgs generate a comment with the exact command line
  arguments that were used to generate the source
  code (default is true)