docs/*/api-types should be generated

[kaovilai]

Describe the problem/challenge you have

Our API Types documentation are manually updated. We should generate them when updating CRD.

ie. https://velero.io/docs/main/api-types/ , https://velero.io/docs/v1.15/api-types/

Describe the solution you'd like

Use https://github.com/ahmetb/gen-crd-api-reference-docs and the likes to update docs when CRD change is detected.
Add to make target for crd.
Add GH Actions to check crd docs in PR is up to date.

Anything else you would like to add:

Environment:

• Velero version (use velero version):
• Kubernetes version (use kubectl version):
• Kubernetes installer & version:
• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):

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