RFC: add `stats/strided/dcurange`

## Checklist

> Please ensure the following tasks are completed before submitting a feature request.

- [x] Read and understood the [Code of Conduct][code-of-conduct].
- [x] Searched for existing issues and pull requests.
- [x] The issue name begins with `RFC:`.

## Description

> Description of the feature request.

This RFC proposes adding support for computing the cumulative range of a double-precision floating-point strided array. This would be a lower-level strided interface which includes a native C implementation and has the following package name:

Package: `@stdlib/stats/strided/dcurange`

## Related Issues

> Does this feature request have any related issues?

None.

## Questions

> Any questions for reviewers?

No.

## Other

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

No.

[code-of-conduct]: https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md

The RFC names @stdlib/stats/strided/dcurange but provides no source files, tests, or implementation entry points. A newcomer would need maintainer guidance to locate the package, establish acceptance criteria, and determine what constitutes completion for the JavaScript-facing package and native C implementation.

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