feat: add shuffle

[iloveitaly]

No description provided.

[Suor]

This makes sense, I would call it shuffled() though akin sorted built-in and to not be confused with random.shuffle(). Also, I would use list(seq) instead of seq.copy() to make it work with arbitrary sequences.

[iloveitaly]

I've updated the PR based on your feedback:

• Renamed shuffle to shuffled to follow Python's naming conventions (like sorted).
• Updated the implementation to use list(seq) instead of seq.copy(), which now correctly handles arbitrary sequences like iterators and ranges.
• Added a docstring to shuffled and updated the documentation in docs/seqs.rst and docs/cheatsheet.rst.
• Verified all tests pass, including a new test case for shuffled with range.