added MergeSort and QuickSort for the java

[attu0]

This pull request adds implementations for two classic sorting algorithms in Java: Merge Sort and Quick Sort. Each algorithm is provided in its own file, complete with a main method for demonstration and testing. The code is well-documented, making it easy to understand the logic and flow of each sorting method.

Sorting algorithm implementations:

• Added a new MergeSort class in MergeSort.java that implements the merge sort algorithm, including detailed comments, a demonstration in the main method, and a Solution helper class for the sorting logic.
• Added a new QuickSort class in QuickSort.java that implements the quick sort algorithm, with a complete test in the main method and helper functions for partitioning, swapping, and printing the array.

[github-actions]

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[github-actions]

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✅ Passed - File naming and structure look good!

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✅ Passed - All code compiles successfully!

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