Create TrappingRainWater

[singhshreya-bhriguvanshi]

Given an array arr[] with non-negative integers representing the height of blocks. If width of each block is 1, compute how much water can be trapped between the blocks during the rainy season.

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• 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 ✅

Project coverage is 64.76%. Comparing base (85b3b1d) to head (b22abcf).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5796      +/-   ##
============================================
- Coverage     64.77%   64.76%   -0.02%     
  Complexity     4295     4295              
============================================
  Files           599      599              
  Lines         16764    16764              
  Branches       3219     3219              
============================================
- Hits          10859    10857       -2     
- Misses         5462     5463       +1     
- Partials        443      444       +1     

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[siriak]

We don't add Leetcode problems