Add label org.opencontainers.image.source

[robinschneider]

Proposed changes

Add label org.opencontainers.image.source to all templates in order for renovate and dependabot to fetch release notes for docker container updates.
https://docs.renovatebot.com/modules/datasource/docker/#description

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[github-actions]

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[robinschneider]

I have hereby read the F5 CLA and agree to its terms

[thresheek]

Hey, not too sure we shall add it

See a previous discussion on that topic: #749

And docker-library/official-images#3540

Seems like annotations are already in place which do the correct source as well: https://oci.dag.dev/?image=nginx