Document master/seed kubernetes version support matrix

KKP version and user-cluster kubernetes version support matrix is documented in
https://docs.kubermatic.com/kubermatic/v2.22/architecture/compatibility/supported-versions

KKP master/seed requirements are documented in
https://docs.kubermatic.com/kubermatic/v2.22/architecture/requirements/cluster-requirements/

But there is no docs page describing master/seed kubernetes version support. The values from go.mod can be used to give some basic idea, for example:
https://github.com/kubermatic/kubermatic/blob/v2.22.2/go.mod#L105
https://github.com/kubermatic/kubermatic/blob/v2.21.2/go.mod#L120
https://github.com/kubermatic/kubermatic/blob/v2.19.0/go.mod#L85

Start with the existing supported-versions and cluster-requirements pages linked in the issue, then compare the referenced go.mod files for the Kubernetes versions used by each KKP release. Add a documentation page or section describing the master/seed Kubernetes version support matrix, and verify that it is linked alongside the existing requirements documentation.

Written by the indexing model from the issue text.