Added documentation around supported-versions configmap

[jparrill]

Which issue(s) this PR fixes
Fixes #HOSTEDCP-794

Checklist

• Subject and description added to both, commit and PR.
• Relevant issues have been referenced.
• This change includes docs.
• This change includes unit tests.

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[enxebre]

Thanks!
/approve

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: enxebre, jparrill

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[openshift-ci]

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[enxebre]

/lgtm