Added mlp_activation_comparison.py

[Karthikn-VR]

Added a new script: mlp_activation_comparison.py

This script demonstrates the effect of different activation functions (relu, tanh, logistic) on a simple dataset using scikit-learn's MLPClassifier.
It helps visualize and understand how activation choices influence model performance.

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Describe your change:

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests?
• Documentation change?

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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. To ease review, I will open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in 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, the description above includes the issue number(s) with a closing keyword (e.g., Fixes #ISSUE-NUMBER).

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