Kaazing Gateway: Enable ARM64v8 support

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

library/kaazing-gateway

@@ -2,3 +2,4 @@
 
 latest: git://github.com/kaazing/gateway.docker@a40c8da9d2c2925bdd78b9a6d1b6da3fe89322d1 
 5.6.0: git://github.com/kaazing/gateway.docker@a40c8da9d2c2925bdd78b9a6d1b6da3fe89322d1
+Architectures: amd64, arm64v8