Feat : Add Dancing Links (DLX) algorithm for Exact Cover problem

[fab-c14]

Describe your change:

This PR adds the Dancing Links (DLX) algorithm for solving the Exact Cover problem, as proposed by Donald Knuth. The implementation is placed in other/dancing_links.py, includes type hints, docstrings, and a usage example. No such algorithm exists in this repo yet.

• Add an algorithm

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.