This PR adds a helper method to consume OCEs when the client disconnects unexpectedly, which is common when the client is a web browser with an open WebSocket connection to the server. ASP.NET Core does not consume these OCEs by default, and since GraphQL over WebSockets can perform any query or mutation that a GET/POST can, it seems that there is no reason why an OCE should be consumed for a WebSocket connection and not for any other connection. Futher, for server-to-server communications, it may be desired to log these exceptions. As such, the default behavior has not been changed. Note that graceful teardown of the WebSocket connection (per WebSocket spec) does not produce an OCE.

See added readme text:

When hosting a WebSockets endpoint, it may be common for clients to simply disconnect rather than gracefully terminating the connection -- most specifically when the client is a web browser. If you log exceptions, you may notice an OperationCanceledException logged any time this occurs.

In some scenarios you may wish to log these exceptions -- for instance, when the GraphQL endpoint is used in server-to-server communications -- but if you wish to ignore these exceptions, simply call app.UseIgnoreDisconnections(); immediately after any exception handling or logging configuration calls. This will consume any OperationCanceledExceptions when HttpContext.RequestAborted is signaled -- for a WebSocket request or any other request.