refactor: update `offset` handling and function documentation for `blas/ext/base/dsnannsumors`

[headlessNode]

Description

What is the purpose of this pull request?

This pull request:

• fix the ndarray function description and the parameter description
• update logic to compute offsetOut
• add the missing float suffx.

Related Issues

Does this pull request have any related issues?

No.

Questions

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No.

Other

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No.

Checklist

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

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

• • *

@stdlib-js/reviewers

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
blas/ext/base/dsnannsumors	$\color{green}411/411$ $\color{green}+100.00\%$	$\color{green}23/23$ $\color{green}+100.00\%$	$\color{green}4/4$ $\color{green}+100.00\%$	$\color{green}411/411$ $\color{green}+100.00\%$

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

[Planeshifter]

/stdlib merge