Add bag datastructure

[kamikkels]

Adding a bag (or multiset/mset) datastructure

See https://en.wikipedia.org/wiki/Multiset for details, or https://algs4.cs.princeton.edu/13stacks/ for the inspiration

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Comments in areas I changed are up to date
• I have added comments to hard-to-understand areas of my code
• I have made corresponding changes to the README.md

[Copilot]

Pull Request Overview

Adds a new Bag (multiset) data structure implementation that allows multiple instances of the same element with multiplicity tracking.

• Implements a generic Bag class with linked list-based storage
• Adds comprehensive test coverage for all bag operations
• Updates README documentation to include the new data structure

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
README.md	Adds Bag to the data structures section
DataStructures/Bag/BagNode.cs	Defines node structure with item, multiplicity, and next pointer
DataStructures/Bag/Bag.cs	Implements the main Bag class with Add, Clear, Count, and enumeration methods
DataStructures.Tests/BagTests.cs	Provides comprehensive unit tests for all bag functionality

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[siriak]

Please act on comments and resolve Codacy issue

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.18%. Comparing base (178d7f9) to head (bb1abc5).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #531      +/-   ##
==========================================
- Coverage   95.20%   95.18%   -0.02%     
==========================================
  Files         272      274       +2     
  Lines       10862    10910      +48     
  Branches     1530     1535       +5     
==========================================
+ Hits        10341    10385      +44     
- Misses        397      400       +3     
- Partials      124      125       +1     

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[siriak]

Looks good, thanks!