Implement Rat in Maze Path Finder

[TruongNhanNguyen]

Description

See details in the implementation

Type of change

• [x] New feature (non-breaking change which adds functionality)

Checklist:

• [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.

[codecov-commenter]

Codecov Report

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

Project coverage is 95.02%. Comparing base (1444e63) to head (1fb1a9e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #730 +/- ## ========================================== + Coverage 95.01% 95.02% +0.01% ========================================== Files 303 304 +1 Lines 22529 22599 +70 ========================================== + Hits 21405 21475 +70 Misses 1124 1124 ```

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