docs: add containerd private registry configuration

[gaius-qi]

Signed-off-by: Gaius [email protected]

Description

• Add containerd private registry configuration.

Related Issue

Fixes #1065

Motivation and Context

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist:

• Code compiles correctly.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[anjia0532]

Chinese docs https://github.com/dragonflyoss/Dragonfly2/blob/main/docs/zh-CN/runtime-integration/containerd/mirror.md