Add shebang to setup.py

[Unike267]

Add shebang to the setup.py file to support installation using:

./setup.py install

Without explicitly specifying the interpreter as Python, the script execution fails (for obvious reasons).

Error:

user@machine:~/path/vunit$ sudo ./setup.py install
[sudo] contraseña para user: 
./setup.py: línea 9: $'\nPyPI setup script\n': orden no encontrada
./setup.py: línea 13: from: orden no encontrada
./setup.py: línea 14: from: orden no encontrada
./setup.py: línea 15: from: orden no encontrada
./setup.py: línea 18: error sintáctico cerca del elemento inesperado `0,'
./setup.py: línea 18: `sys.path.insert(0, str(Path(__file__).parent.resolve()))'

By adding the appropriate shebang, the interpreter will be correctly identified, ensuring the script runs as expected.

Cheers!

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/cc @umarcor