chore: update docs and tests of blas/ext/base/dapxsum

[headlessNode]

Description

What is the purpose of this pull request?

This pull request:

• update documentation and test case for stride equal to zero.

Related Issues

Does this pull request have any related issues?

No.

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

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-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/dapxsum	$\color{green}349/349$ $\color{green}+100.00\%$	$\color{green}13/13$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}349/349$ $\color{green}+100.00\%$

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

[kgryte]

LGTM. Thanks, @headlessNode!