Avoid void returning asynchronous method

Identifier: ASYNC0003

Default Action: Warning

Rationale: When an async void method is called execution flow continues as opposed to having a Task returning method and awaiting it. This fire and forget behaviour is not usually what one wants. Async void methods should only be used for event handlers and in exceptional fire and forget cases. However if one is used make sure it is at least wrapped in a try catch block to avoid exceptions going unhandled.