[Docs]: developer guide to adopting and migrating to Tachyon

We currently have some high level information about tachyon in Altis: https://docs.altis-dxp.com/media/dynamic-images/ this is all a lot of engineers may need; but in order to develop a series of more practial guides, I think it could be really good to offer a guide on what problems tachyon solves, and how to migrate to tachyon, what to be aware of, etc.