Introduce docs directory

[nirs]

We want to add more workloads (stalefulset, daemonset), more storage (CephFS), and the new OCM discovered applications.

Each variant require specific instructions or example commands so it is best done using one file per variant, where you can experiment with complete disaster recovery flow for a single variant.

• Move the content we had in the main README.md to docs/initial-setup.md and docs/ocm-rbd.md
• Move the content we had in workloads/kubevirt/README.md to docs/ovm-kubevirt.md.
• Add docs/create-environment.md with short instructions how to create a testing environment for playing with the samples in this repo.
• Change README.md to a short overview linking to all other documents.

The new docs directory can be used next to create more structure documentation like https://docs.readthedocs.io.

Preview: https://github.com/nirs/ocm-ramen-samples/tree/ec49e1159dbe80e13a0c7927653f739a82973356

[nirs]

Changes in latest version:

• Rebase on master, including latest changes regarding disable dr.