Ratify repo migration guide for users

[susanshi]

What would you like to be added?

We need to document all user actions needed after the repo move.

Anything else you would like to add?

No response

Are you willing to submit PRs to contribute to this feature?

• Yes, I am willing to implement it.

[akashsinghal]

Starting in v1.3.0, ratify's go pkg will be published under github.com/ratify-project domain instead of github.com/deislabs. Any package importing ratify's pkgs MUST move to the new pkg name in order to receive new versions of ratify pkgs.