Added RHEL/Rocky install instructions (PyPI). Instructions cover
versions 8 and 9 which are the only supported ones - except for RHEL7
which is now on extended life cycle support phase.
Large part of the guide is for installing Python 3.11 or 3.12. RHEL8
ships with Python 3.6 and RHEL9 ships with 3.9. Newer Python versions
can be installed easily as they don't interfere with OS software that
still relies on the default Python version.
I was first planning to add prerequisites part to the prerequisites
section and then install instructions on the top of the page but that
section is for pre-built packages so it just didn't sound right. So I
just dumped everything to the PyPI section of the page. But suggestions
to change are welcome.
I also didn't combine these with Fedora section. I haven't tested those
packages on RHEL and Fedora ships with Python 3.12 out-of-box.
