Archive Flux v1 example repositories

[stefanprodan]

With Flux v2 approaching GA, new users get confused of which examples to use.

I propose we update https://github.com/fluxcd/flux-get-started and https://github.com/fluxcd/flux-kustomize-example with:

In preparation of Flux v2 GA this repository with Flux v1 examples has been archived. The Flux v2 equivalent of what is shown here can be found at flux2-kustomize-helm-example.

And https://github.com/fluxcd/multi-tenancy with:

In preparation of Flux v2 GA this repository with Flux v1 examples has been archived. The Flux v2 equivalent of what is shown here can be found at flux2-multi-tenancy.

After the readme update, we could archive these repos.

[dholbach]

High five @hiddeco and @stefanprodan