Add Merge Intervals algorithm

[Hardvan]

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

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

Project coverage is 52.33%. Comparing base (0bd86b3) to head (3eb9307).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5516      +/-   ##
============================================
+ Coverage     52.29%   52.33%   +0.03%     
- Complexity     3257     3258       +1     
============================================
  Files           525      526       +1     
  Lines         15185    15192       +7     
  Branches       2887     2889       +2     
============================================
+ Hits           7941     7950       +9     
+ Misses         6920     6919       -1     
+ Partials        324      323       -1     

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[Hardvan]

Thanks!