Add a basic *stateful* migration scenario of a single well known application

[istein1]

Add a basic stateful migration scenario of a single well known application:
Maybe consider using https://github.com/konveyor-ecosystem/kubectl-migrate/tree/main/sample-resources.

Note we already have initial drafts for this, suggested in PR #310:
stateful-migration-tutorial.md.
Path in Crane tree:
crane/
├── CONTRIBUTING.md
├── README.md (updated with docs links)
└── docs/
├── README.md
├── development/{README, architecture, setup, testing, plugin-development}.md
├── commands/{export, transform, apply, validate, transfer-pvc}.md
├── installation.md
├── multistage-pipeline.md
├── migration-paths.md
├── plugins.md
├── state-migration.md
├── quickstart-tutorial.md
├── stateless-migration-tutorial.md
├── stateful-migration-tutorial.md
├── troubleshooting.md
├── pre-apply-validation-guide.md
└── resource-compatibility.md

This is related to #215 but is not blocking it.

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