* Produce a better error message when the destination org doesn't exist.
* Support pushing to the authenticated user's account
**Before**
`error creating github repository `synced-actions/setup-node`: error creating repository: POST http://my-ghes-hostname/api/v3/orgs/synced-actions/repos: 404 Not Found []`
**After**
`error creating github repository `synced-actions/setup-node`: Organization `synced-actions` doesn't exist at http://my-ghes-hostname. You must create it first.`
https://github.com/actions/actions-sync/issues/1
