feat: add stats/incr/nanmhmean

[satansin123]

Resolves #5577.

Description

What is the purpose of this pull request?

This pull request:

• Adds the @stdlib/stats/incr/nanmhmean package, which computes an incremental mean while handling NaN values by skipping them.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves [RFC]: add stats/incr/nanmhmean #5577

Questions

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No.

Other

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tests -

benchmark -

examples -

Checklist

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• Read, understood, and followed the contributing guidelines.

---

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Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanmhmean	$\color{green}178/178$ $\color{green}+100.00\%$	$\color{green}11/11$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}178/178$ $\color{green}+100.00\%$

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

[satansin123]

/stdlib help

[stdlib-bot]

@satansin123, available slash commands include:

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• /stdlib update-copyright-years - Update copyright header years.
• /stdlib lint-autofix - Auto-fix lint errors.
• /stdlib merge - Merge changes from develop branch into this PR.
• /stdlib rebase - Rebase this PR on top of develop branch.

[satansin123]

/stdlib lint-autofix