Release v2.16.0

Added

• Add support for SSO errors coming from the API (eiriksm) #913
• Add OutsideCollaborators api (Matth--) #925
• Add support for creating a repo dispatch event (Nyholm) #931

Changed

• Fix: Wrong PHPDoc description (OskarStark) #922
• Adding GitHub authentication to GraphQL documentation (legionth) #927

Fixed

• Use RFC3986 for building URI query strings (GrahamCampbell) #908
• Fix call to test a webhook method (morrislaptop) #915