refactor: improve type specificity for `utils/group-own`

[Shubh942]

Resolves #1085

Description

What is the purpose of this pull request?

This pull request:

• Adds generics for improved type safety for the group-own function.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves stdlib-js/stdlib/issues/1085

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.

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

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@stdlib-js/reviewers

[Shubh942]

@Planeshifter @kgryte please review this pr

[Planeshifter]

@Shubh942 Thanks for your efforts, but as-is this cannot be merged due to various issues:

• it incorrectly removes the options parameter from the function signature (notice that the returns option also influences the shape of the returned output, see the README.md)
• irrespective of that, it assumes that the values of the returned record are all string arrays (string[]); while true for the example code, the function is not limited to string values.

[Shubh942]

@Planeshifter I have made the changes.

[Shubh942]

@Planeshifter would you please review this PR