### Description of Change

in AudioEngine.cs, the second constructor uses `TimeSpan lookAheadTime`
and `string rendererId`, which are never used. I presume these were left
in a long time ago, but now they can only deceive people by promising
features that do not exist.

1) Removed parameters from the constructor that are not in use (causing
AudioEngine to only have 1 constructor now)
2) Added a small bit of missing documentation to the method and removed
documentation that is no longer needed.
3) Turned ArgumentNullException into ArgumentException (one should throw
ArgumentException for empty/null strings, not ArgumentNullException
which is specifically for ``null` only. See also
https://learn.microsoft.com/en-us/dotnet/api/system.argumentexception.throwifnullorempty)