added prim's algorithm

[ShristiC7]

Describe your change:

• Add an algorithm — Prim’s Minimum Spanning Tree (MST) algorithm in Python.

This implementation demonstrates how to construct a MST for a connected, undirected, weighted graph using Prim’s algorithm. The code is accompanied by doctests to verify correctness and includes type hints for all functions and parameters.

Reference: Prim’s algorithm - Wikipedia

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Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work — I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes Added Prim's Algorithm #13539 .

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Example Doctest:

>>> graph = {
...     'A': {'B': 2, 'C': 3},
...     'B': {'A': 2, 'C': 1},
...     'C': {'A': 3, 'B': 1}
... }
>>> prim_mst(graph)
{'B': 'C', 'C': 'B', 'A': 'B'}

[ShristiC7]

Solves issue

• added prim's algorithm #13540
• Added Prim's Algorithm #13401
  @cclauss

[cclauss]

• graphs/minimum_spanning_tree_prims.py
• graphs/minimum_spanning_tree_prims2.py
• graphs/prim.py