Allow synchronous methods to have the suffix 'Synchronously'

[sharwell]

Closes #331

[AArnott]

In #331 you said Roslyn follows this pattern:

T SomeMethodSynchronous();
Task<T> SomeMethodAsync();

Notice that the suffix is Synchronous whereas this PR recognizes Synchronously (-ly ending).

So is this really fixing anything?

[sharwell]

The suffix used there is Synchronously:

https://github.com/dotnet/roslyn/blob/f2c441274de1620496975ee223ec255c13bcafaa/src/Workspaces/Core/Portable/Workspace/Solution/TextDocument.cs#L83

It's unclear whether Synchronous should be allowed as well.

[AArnott]

I'm going to close due to the build validation failure, the merge conflicts, and the open question on the original issue. Let's follow up on the issue and either close that, or re-open this PR when it's ready.