Added Merge k Sorted List Solution in Java

[Dhairyati]

Added "Merge K Sorted Linked Lists" problem solution in Java

Description:
This PR adds a solution for the "Merge K Sorted Linked Lists" problem under the dsa_in_java/linkedlist/ folder.
The code merges multiple sorted linked lists into a single sorted linked list using a Min-Heap (PriorityQueue) approach.

The file follows the required contribution format — including problem description, approach, time and space complexity, and example input/output.

Related Issue:
Solution for issue: #303

✅ Checklist

• My code follows the project guidelines.
• I have tested the changes locally.

[github-actions]

🧩 PR Checklist

Hi @Dhairyati, before merging please ensure:

• Updated contributor.md
• Added proper commit message
• Verified build/test success ✅

[github-actions]

⚠️ @Dhairyati, please add your details to the contributor.md file before merging. 🙏

[HarshitPachori]

@Dhairyati please update the contributor.md file

[Dhairyati]

@HarshitPachori
My name is already listed in the Contributors.md file from a previous contribution (Recipe Finder project), so I haven’t added it again for this PR.

[ayushHardeniya]

@Dhairyati you need to update your respective PR into Contributors.md as onle line update - what ever you're updating or adding with the PR.

[HarshitPachori]

@Dhairyati if your name is already in the contributor.md , then you have to just add the description of your commit under your name.
Like previously you worked on recipe finder but now you worked on merge k sorted . Therefore you might need to uodate the file by adding something like - added problem code for merge k sorted ..... In java language.

[ayushHardeniya]

Closed after inactivity, and no response from the author.