Minor errors/typos in documentation

[WagnerChristoph]

Issue found on May 06th 2020.

1. In object model definition of saved show the show object should be a simplified show object (As correctly stated in https://developer.spotify.com/documentation/web-api/reference/library/get-users-saved-shows/).

2. The ids query parameter in Save Shows for Current User Request does not have a maximum number of ids.

3. In the object model definition of playlist track the description of the key track is missing an "n" at "a track object or an episode object"

4. In the Context object in the response of Get Information About The User's Current Playback Request and Get the User's Currently Playing Track the key type can also be show.