Implement Knight Tour algorithm using Backtracking.

[sozelfist]

Description

This PR implements the Knight's Tour algorithm in Rust, along with unit tests and documentation updates.

Type of change

• [x] New feature (non-breaking change which adds functionality) :rocket: The purpose of this PR is to add the Knight's Tour algorithm to the project, which solves the classic chess problem of finding a sequence of knight moves that visits every square of a chessboard exactly once. By adding this algorithm, we enhance the project's functionality and provide a useful feature for users who are interested in chess algorithms.

Checklist :heavy_check_mark:

• [x] I ran bellow commands using the latest version of rust nightly.
• [x] I ran cargo clippy --all -- -D warnings just before my last commit and fixed any issue that was found.
• [x] I ran cargo fmt just before my last commit.
• [x] I ran cargo test just before my last commit and all tests passed.
• [x] I added my algorithm to the corresponding mod.rs file within its own folder, and in any parent folder(s).
• [x] I added my algorithm to DIRECTORY.md with the correct link.
• [x] I checked COUNTRIBUTING.md and my code follows its guidelines.

Additional Notes :pencil2:

This PR includes comprehensive unit tests for the Knight's Tour algorithm, covering various edge cases and scenarios. Additionally, the algorithm is well-documented to help users understand its functionality and usage.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.53%. Comparing base (d5157e6) to head (d601549).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #695 +/- ## ========================================== + Coverage 94.51% 94.53% +0.01% ========================================== Files 293 294 +1 Lines 21854 21919 +65 ========================================== + Hits 20656 20721 +65 Misses 1198 1198 ```

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[sozelfist]

Let's have a final look @vil02