Update README.md for move to kodi.config.
Update README.md for move to kodi.config.

Note that this doesn't yet document how to configure a given Echo device
to talk to a particular Kodi instance.  This is just to document the
migration to kodi.config.

digiltd/kodi-alexa,m0ngr31/kodi-alexa,ta264/kodi-alexa,jingai/kodi-alexa,ausweider/kodi-alexa