Slightly improve docker description

Change-Id: I6337ec80baa760bda721ec0a6be8099304995cfd
diff --git a/Dockerfile b/Dockerfile
index 2a877b3..260c5cc 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -72,6 +72,6 @@
 
 CMD [ "daemon" ]
 
-LABEL author="korap@ids-mannheim.de"
+LABEL maintainer="korap@ids-mannheim.de"
 LABEL description="Docker Image for Kalamar, the KorAP user frontend"
 LABEL repository="https://github.com/KorAP/Kalamar"