The VSTS Extension Tasks are a set of tasks for Team Build and Release Management to package, publish, share and install extensions to your Visual Studio Team Services account or TFS 2015 update 2 server.
There are quite a few people using the extension to package and publish their Visual Studio Team Services and TFS extensions.
There's a few places with more information on how to use them:
I'm using these tasks to package and publish my other build tasks:
A few other MVPs/Rangers that are using these tasks include Richard Fennel, Rene van Osnabrugge, Peter Groenewegen and Utkarsh Shigihalli and others.