refactor: updating js implementation in stats/base/cumax

[vivekmaurya001]

Description

• refactors JS implementation for @stdlib/stats/base/cumax along with benchmarks and examples to follow latest conventions
• used defined ndarray function instead of defining a new function
• updated the readme file , package.json , benchmark.c , examples.c

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-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
stats/base/cumax	$\color{green}244/244$ $\color{green}+100.00\%$	$\color{green}20/20$ $\color{green}+100.00\%$	$\color{green}2/2$ $\color{green}+100.00\%$	$\color{green}244/244$ $\color{green}+100.00\%$

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

[vivekmaurya001]

@Planeshifter, @gunjjoshi , @kgryte please take a look