README does not mention s390x nor RHEL9 support

[hseipp]

Describe the bug
The README, OS support section specifies

OS support

    Support for RHEL 7 on x86_64, PPC64 and PPC64LE
    Support for RHEL 8 on x86_64 and PPC64LE
    Support for UBUNTU 20 on x86_64 and PPC64LE
    Support for SLES 15 on x86_64 and PPC64LE

but neither s390x nor RHEL9.
Both are supported with the Ansible-based installer as delivered with Scale 5.1.8, so the clients expect the same to be delivered and documented with this project.

To Reproduce
Steps to reproduce the behavior:

1. Read the README file
2. Compare with the GPFS FAQ supported platforms Section 2.1

Expected behavior
The platform support for s390x and RHEL9 needs to be added. If there are any limitations, they should be mentioned. Platform-specifics like the vmalloc setting need to be added.

Environment
Storage Scale 5.1.8, s390x, RHEL 9.2