Missing IScheduler parameter

Missing Scheduler

Adds a hint highlight to methods which have an overload taking an IScheduler parameter. This is highlighted because not defining an explicit IScheduler instance can cause issues when testing and more importantly can cause threading issues such as deadlocks.

Most method which define overloads that take an IScheduler parameter usually define the default value to be 'Immediate', unfortunately there doesn't appear to be a list defining the default for the extension method in the Reactive Extensions libraries.