Consider returning subprocess.CompletedProcess instance from Engine1D.run()

It would be cool if `Engine1D.run()` returned the `subprocess.CompletedProcess` instance that is returned from the `subprocess.run()` call at https://github.com/DHI/mikepluspy/blob/69d0bdd6e35657b9d7911948a3dcb5b546612285/mikeplus/engines/engine1d.py#L49. This would allow users to check for subprocess errors within a script, if running a loop for instance.

https://docs.python.org/3/library/subprocess.html#subprocess.CompletedProcess

Open mikeplus/engines/engine1d.py around line 49 and inspect the subprocess.run() call referenced in the issue. Read Python's subprocess.CompletedProcess documentation to confirm the expected return value. Done means Engine1D.run() exposes that result so callers can inspect subprocess errors while looping.

Written by the indexing model from the issue text.