Clarify support for `choices` as int in HSSM class

[cpaniaguam]

The docstring says choices can be an int (number of choices), but HSSM.__init__ types it as list[int] | None and it's not clear where the logic for creating the actual list of choices is.

HSSM/src/hssm/hssm.py

Lines 115 to 121 in 3654d2d

	choices : optional
	When an `int`, the number of choices that the participants can make. If `2`, the
	choices are [-1, 1] by default. If anything greater than `2`, the choices are
	[0, 1, ..., n_choices - 1] by default. If a `list` is provided, it should be the
	list of choices that the participants can make. Defaults to `2`. If any value
	other than the choices provided is found in the "response" column of the data,
	an error will be raised.

[cpaniaguam]

@digicosmos86