doc: how to exclude sidecar images in policies

[ritazh]

Describe the solution you'd like
[A clear and concise description of what you want to happen.]
especially for the service mesh use cases

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Gatekeeper version:
• Kubernetes version: (use kubectl version):

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.