Add PyTorch to requirements

[flferretti]

This PR adds PyTorch explicitly to the requirements. It was not listed in the pyproject.toml, but during the import the code checks for torch installation

dex-retargeting/src/dex_retargeting/__init__.py

Lines 3 to 8 in 3f56141

	if find_spec("torch") is None:
	raise ImportError(
	"Torch is not installed. You can install it using the following command:\n"
	"pip install torch --index-url https://download.pytorch.org/whl/cpu\n"
	"Note that cpu-only torch already works for dex-retargeting."
	)