Issue Summary

Unify the version indication of the documentation between Atlassian Developer (https://developer.atlassian.com) and Confluence Support (https://confluence.atlassian.com)

While referencing the REST API documentation, we noticed it would be helpful to have a clear indication of which Confluence version is available for which REST API endpoint.

This is an example of how it looks like for the Atlassian Developer REST API documentation:

• https://developer.atlassian.com/server/confluence/rest/v920/intro
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This is an example of how it looks like for the Confluence Support documentation:

• https://confluence.atlassian.com/conf93/upgrading-confluence-1502351635.html
• 

One of the good ways that we can unify the version indication of the documentation between Atlassian Developer (https://developer.atlassian.com) and Confluence Support (https://confluence.atlassian.com). Please refer to the example in the screenshot below: