offload: add initial docs (#22910)
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## Description
Add initial Docker Offload docs
https://deploy-preview-22910--docsdocker.netlify.app/offload/
https://deploy-preview-22910--docsdocker.netlify.app/reference/cli/docker/offload/
https://deploy-preview-22910--docsdocker.netlify.app/desktop/setup/vm-vdi/
Minor changes
https://deploy-preview-22910--docsdocker.netlify.app/desktop/
https://deploy-preview-22910--docsdocker.netlify.app/
https://deploy-preview-22910--docsdocker.netlify.app/manuals/
Pending sign up page link.
## Related issues or tickets
ENGDOCS-2704
## Reviews
<!-- Notes for reviewers here -->
<!-- List applicable reviews (optionally @tag reviewers) -->
- [ ] Technical review
- [ ] Editorial review
- [ ] Product review
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Signed-off-by: Craig <craig.osterhout@docker.com>
