Added s390x to Supported platforms

added s390x to supported platforms section in readme. Marked it as Experimental

Signed-off-by: Eddy (Eduard) Stefes <eddy@linux.ibm.com>

Author: fneddy

README.md

@@ -21,6 +21,7 @@ Supported host architectures:
 - Little-endian x86_64
 - Little-endian aarch64
 - Little-endian riscv64
+- Big-endian s390x (*Experimental*)
 
 ## Short seccomp tutorial