feat(lib): add stats/incr/nanmmax

[ivishal-g]

Resolves #5584.

Description

This pull request adds a new incremental statistics package @stdlib/stats/incr/nanmmax, which provides an accumulator function that computes a cumulative maximum while correctly ignoring NaN values (similar to nanmin, nansum, etc.).

The implementation properly handles signed-zero edge cases and returns null until the first non-NaN value is observed.

Related Issues

This pull request resolves #5584.

Questions

No.

Other

No.

Checklist

• Read, understood, and followed the [contributing guidelines][contributing].

AI Assistance

• Yes
• No

If you answered "yes" above, how did you use AI assistance?

• Code generation (e.g., when writing an implementation or fixing a bug)
• Test/benchmark generation
• Documentation (including examples)
• Research and understanding

Disclosure

I used Grok (xAI) to help troubleshoot and fix numerous lint errors (markdown, JSDoc, ESLint rules, REPL help, examples, etc.) and to ensure the implementation and documentation match stdlib’s style. The final code, README, and examples were reviewed and adjusted manually.

---

@stdlib-js/reviewers
[contributing]: https://github.com/stdlib-js/stdlib/blob/develop/CONTRIBUTING.md

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmmax	$\color{green}132/132$ $\color{green}+100.00%$	$\color{green}14/14$ $\color{green}+100.00%$	$\color{green}2/2$ $\color{green}+100.00%$	$\color{green}132/132$ $\color{green}+100.00%$

The above coverage report was generated for the changes in this PR.