Consider move azure devops extensions overview doc files

[unaizorrilla]

Hi @lfraile

AzureDevOps extensions overview is not included on our docs directory, used by ReadTheDocs!, can you consider moving the overview.md into doc folder or create a new walkthrought on this topic?

Thanks

[lfraile]

I will create a new walkthrough. Can't change the file (think so) due to extension packaging