add Three sum

[BamaCharanChhandogi]

Describe your change:

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

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.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

[algorithms-keeper]

Click here to look at the relevant links ⬇️

🔗 Relevant Links

Repository:

• Contributing guidelines
• Project Euler solution guidelines

Python:

• Formatted string literals (f-strings)
• Type hints
• doctest
• unittest
• pytest

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[algorithms-keeper]

Variable and function names should follow the snake_case naming convention. Please update the following name accordingly: threeSum

[BamaCharanChhandogi]

@cclauss can you check?

[cclauss]

Is there any practical use for this algorithm?

[cclauss]

Please put the uses in the docstring where they will be seen, not in these review comments where they will be lost.

[BamaCharanChhandogi]

Please put the uses in the docstring where they will be seen, not in these review comments where they will be lost.

OK, I will add in docstring.

[BamaCharanChhandogi]

hello @cclauss, Next Please give a review.

[BamaCharanChhandogi]

Hey @dhruvmanila @cclauss, I have a question after merging this PR why are 2 checks passed?
I have done it for Hacktoberfest 2023, There are not showing successfully merged PR.