Make Wolverine aware of Task<unit>

[nkosi23]

Is your feature request related to a problem? Please describe.
unit is the equivalent of void in F#, and F# tasks typically return a Task[unit] instead of returning a Task. The problem is, Wolverine ignores handlers returning a Task. This results in 404 responses.

Describe the solution you'd like
Wolverine automatically discovers handlers returning a Task

Describe alternatives you've considered
Casting Task[unit] into a task, but this is a little tedious to do every time even though this issue is relatively minor overall since returning nothing is relatively rare.