Summary of the new feature/enhancement

While Start-Sleep -MilliSeconds offers fine-grained control over the sleep duration, it would be convenient not to have two switch parameters just to be able to effectively specify fractional seconds.

E.g., instead of:

Start-Sleep -MilliSeconds 1400

it would be nice to be able to write:

Start-Sleep 1.4  # wishful thinking; translate into 1,400 msecs.

This is in line with the sleep utility on macOS and Linux, which accepts fractional values (e.g., sleep 1.4)

Currently, fractional values are quietly converted to [int] values, which means that rounding is applied, which is not only obscure behavior, but behavior that existing code is unlikely to rely upon.

As an aside: Start-Sleep is misnamed and should be called Invoke-Sleep - see #3990.

Proposed technical implementation details (optional)

Change the data type of the -Seconds parameter from [int] to [double] and simply cast the internal conversion to milliseconds to (int).