v12.12.0

• Domain::setup and constructors receive the key they were mounted at via
  options.key.
• Added prepare prop for ActionButton that allows developers to specify
  an extra transformation of the underlying value (e.g. based on the event
  object) before the action gets dispatched.
• Domain and effect registration handlers can be an array of functions
  that are processed sequentially.
• Tweaked internal processing of actions to allow function arguments
  to be returned from actions without being treated as a thunk. See
  the docs for Actions for more information.