Merge sort: I implemented the merge-sort algorithm in Python

[MurtazaHakimi]

To solve the problem, I implemented the merge-sort algorithm in Python, providing two versions (mergesort_v1 and mergesort_v2). The mergesort_v1 function recursively splits the input array, sorts its halves, and then merges them. The mergesort_v2 function adopts a more concise approach, utilizing the built-in sorted function for merging. Both functions ensure correct sorting for edge cases, such as an empty array or a single element. The test script (test_merge_sort.py) validates the correctness of these implementations through various test cases, covering scenarios of an empty array, single-element arrays, arrays in increasing, decreasing, and random orders. -->

• [x] PR's title includes the challenge's name and language
• [x] PR has short and clear description of the challenge
• [x] PR has appropriate labels and milestones for easy identification
• [x] PR it is assigned to the owner
• [x] reviewers are assigned
• [x] the PR contributes only one focused change
• [x] the branch is up to date with main/master
• [x] the code works when pulled and run locally
• [x] all conflicts are resolved (if any)
• [ ] It is linked to an issue in the appropriate column of the project board
• [ ] feedback is addressed (if any, and if it is appropriate feedback.)

README Documentation

• [ ] The solution is documented in /src/README.md
• [ ] The markdown source is formatted
• [ ] Spelling and grammar is correct in all text
• [ ] The markdown looks correct when you preview the file
• [ ] All links and images work
• [ ] The README documents the solution's behavior, strategy(ies) and implementation(s)
• [ ] There are use cases in code blocks to illustrate the function's behavior

Python Files

• [ ] There is a module header
• [ ] There is a module docstring
• [x] File names are in snake_case
• [x] Test files are named test_<module_name>.py

Function Docstring

• [ ] Behavior description
• [ ] Parameter description
• [ ] Return value description
• [ ] Include any assumptions
• [ ] Include 3 or more (passing!) doctests
• [ ] Include 1-2 use cases (if necessary)

Function Implementation

• [x] The solution is not is not copied from djeada
• [x] The code is auto-formatted
• [x] The code has no (reasonable) linting mistakes
• [ ] Variables are named with snake_case
• [ ] The function has a clear and helpful name
• [x] The file's name matches the function name
• [x] The code follows the strategy as simply as possible
• [x] Variable names are clear and helpful
• [ ] Comments explain the strategy (if necessary)
• [ ] There are type annotations
• [ ] (challenge) The code includes defensive assertions

Unit Test Suite

• [x] The test class has a helpful name in PascalCase
• [ ] The test class has a docstring
• Each unit test has
  • [x] A helpful name
  • [x] A clear docstring
  • [x] Only one assertion
• [x] All tests pass
• [x] There are tests for defensive assertions
• [x] There are tests for boundary cases
• [x] Test suite includes black-box and glass-box tests

[YaninaChukanova]

Please delete unnecessary files, as there are each task should have the appropriate files and add READMY with Documentation

Function Docstring Behavior description (Doesnt have, Need to add) Parameter description(Doesnt have, Need to add) Return value description(Doesnt have, Need to add) Include any assumptions(Doesnt have, Need to add)

Unit Test Suite The test class has a docstring ( Doesn`t have, Need to add)