add "2.4.0" to the list

README.md

@@ -97,7 +97,7 @@ wget --post-file=example.xml --header="Content-Type:text/xml;" -q -O- http://loc
 ```shell
 curl -X POST -H "Content-Type: text/xml?v=2.1.0" -d @no_valid_xml http://localhost:5005/validate
 
-<error>unvalid xml data</error>
+<error>invalid xml data</error>
 ```
 
 ```shell

server.py

@@ -69,7 +69,7 @@ def validation():
     l = str(request.accept_languages).split(',')[0][0:2]
     if l != 'de':
         l = 'en'
-    x = "['2.3.0','2.2.0','2.1.1','2.1.0']"
+    x = "['2.4.0','2.3.0','2.2.0','2.1.1','2.1.0']"
     return trans.show_html(version=utils.get_version(), language=l, 
       xsd_versions=x)