feat: add stats/incr/nanewmean

[abhishekblue]

Resolves #5556

Description

What is the purpose of this pull request?

This pull request:

• introduces the @stdlib/stats/incr/nanewmean package, which incrementally computes an exponentially weighted mean, ignoring NaN values.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves [RFC]: add stats/incr/nanewmean #5556

Questions

Any questions for reviewers of this pull request?

No.

Other

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No.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/incr/nanewmean	$\color{green}131/131$ $\color{green}+100.00\%$	$\color{green}7/7$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}131/131$ $\color{green}+100.00\%$

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

[hrshya]

You need to import isnan from @stdlib/math/base/assert/is-nan and replace isNaN with isnan in main.js and other files.

[abhishekblue]

@hrshya Thank you for pointing out.