Add A* Search algorithm for shortest path

[bhoomika1714]

• Implemented A* Search for shortest pathfinding.
• Supports weighted graphs.
• Includes example usage in main().
• Useful for games, robotics, and navigation.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.36%. Comparing base (bb6385e) to head (6a307fa).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6987   +/-   ##
=========================================
  Coverage     78.35%   78.36%           
  Complexity     6615     6615           
=========================================
  Files           746      746           
  Lines         22015    22015           
  Branches       4320     4320           
=========================================
+ Hits          17249    17251    +2     
+ Misses         4078     4077    -1     
+ Partials        688      687    -1     

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