Add get_word_path function to word_search.py

[kadambari25]

Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests?
• Documentation change?

Implemented a new function get_word_path in backtracking/word_search.py.

This function returns the list of coordinates (row, column) representing the path of the given word in the board instead of just returning a boolean value.

• Uses backtracking (DFS) approach
• Returns list of tuples if the word is found
• Returns None if the word does not exist

Fixes #14500

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.
• 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.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.