Document new branching steps

[mateusoliveira43]

When a new branch (for a new OADP version) is created, some steps must be made. Document these steps.

• add mirrors to promoted 1.3 images from ci registry to quay #1233

References:

• [oadp-1.3] fix: Update operator CSV for version 1.3.0 #1226
• OADP: Add E2E tests for branch oadp-1.3. release#45664
• Add OADP 1.3 branch to the velero and velero plugins. release#45692
• TODO restic CI PR
• Do not forget to metion vsm/volume-snapshot-mover for branches < 1.3
• add information about this file in CI docs https://github.com/openshift/release/blob/master/core-services/image-mirroring/konveyor/mapping_konveyor_latest
• talk about order and circular dependencies... fix: OADP 1.3 mirror images release#45811

[kaovilai]

Do not forget to metion vsm/volume-snapshot-mover for branches < 1.3

Don't think we would be branching unless we're making new versions

[mateusoliveira43]

Will finish this one first #1237 before working on this issue

[mateusoliveira43]

Talk about build/ci-dockerfile https://github.com/search?q=repo%3Aopenshift%2Frelease%20ci-Dockerfile&type=code

[mateusoliveira43]

add link to flake list https://github.com/openshift/oadp-operator/wiki/FRIGGIN-TIGER-FLAKES

[mateusoliveira43]

update this as well https://github.com/openshift/oadp-operator/blob/master/Makefile#L441

[mateusoliveira43]

also talk about cron in periodic jobs

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[mateusoliveira43]

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