v6.0.0

• #537: Add an interface for websocket specific transport methods by @ben-voss
• #539: Add support for the graphql-transport-ws websocket protocol and default to protocol auto-negotiation by @joao-avelino, @rose-a
• #542: Allow configuring the default UserAgent header by @KirovAir, @rose-a
• Update dependencies and cleanup code formatting by @sungam3r

Breaking Changes

• The signature of IGraphQLJsonSerializer has changed to support different websocket payload types
• The client now negotiates the websocket protocol with the server by default. The used websocket protocol can be forced by setting GraphQLHttpClientOptions.WebSocketProtocol