[flux] Add supported versions per releaseCycle

[BiNZGi]

Saw today that documentation lists supported versions of Kubernetes and OpenShift, see https://fluxcd.io/blog/2024/05/flux-v2.3.0/#supported-versions

Distribution	Versions
Kubernetes	1.28, 1.29, 1.30
OpenShift	4.15

-> These details can be added as customColumns to https://endoflife.date/flux

Also found this https://fluxcd.io/flux/releases/#kubernetes-supported-versions:

The Flux CLI and controllers offer support for all Kubernetes versions supported upstream.

Every Flux release undergoes a series of conformance and end-to-end tests for the latest Kubernetes minor release. The test suite is run against Kubernetes Kind for both AMD64 and ARM64 distributions.

We expect users to keep Kubernetes up-to-date with the latest patch version of a supported minor release. Once a Kubernetes version reaches end-of-life, we can’t guarantee the next Flux release will work with it, as we don’t run end-to-end testing for EOL Kubernetes versions.

😍 for linking endoflife.date

-> We can add some details with a link to that.