Kazzing Gateway: Use easy to reference versioning

Instead of using only '5.6.0', also provide '5.6' and '5' options as
suggested in:

  https://github.com/docker-library/official-images#tags-and-aliases

Signed-off-by: Lee Jones <[email protected]>

library/kaazing-gateway

@@ -1,6 +1,6 @@
 Maintainers: Kaazing Docker Maintainers <https://github.com/kaazing/gateway.docker/issues> (@kaazing)
 
-Tags: 5.6.0, latest
+Tags: 5.6.0, 5.6, 5, latest
 Architectures: amd64, arm64v8
 GitRepo: https://github.com/kaazing/gateway.docker.git
 GitCommit: a40c8da9d2c2925bdd78b9a6d1b6da3fe89322d1