Add selected optional ndarray features (focused, high-value extensions)

[YassineSamirX]

Description

Implement a small set of optional ndarray features inspired by NumPy, after mandatory features are stable.

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Important Rule

• Add only meaningful features.
• Avoid many near-duplicate functions with little added value.

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Candidate Directions

• Universal functions (ufunc-style operations)
• Broadcasting for operations on different shapes
• Other useful NumPy-inspired features

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Tasks

• Select 1–2 optional features with clear added value
• Define exact behavior and edge cases before coding
• Implement feature(s) with minimal API complexity
• Add unit tests for normal and failure cases
• Verify no regression on mandatory features
• Document new feature(s) in README with examples

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Done When

• Optional feature(s) are clearly useful and not redundant
• Tests pass locally and in CI
• Mandatory feature behavior remains stable
• README explains usage and limitations of added feature(s)

[YassineSamirX]

I added 2 features : scalar addition and sum reduction.

I'm not sure if I will add more for now so i will close the issue.
I will reopen it if I decided to work more on it.

review the PR please