[RFC]: add `array/base/broadcasted-quinary3d`

### Description

This RFC proposes adding a new package to the `array/base/*` namespace: `@stdlib/array/base/broadcasted-quinary3d`.

This package is the quinary equivalent of [`@stdlib/array/base/broadcasted-binary3d`](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/broadcasted-binary3d).

To provide a concrete example of what a PR adding the desired package should contain, see [`@stdlib/array/base/broadcasted-quinary2d`](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/broadcasted-quinary2d), which is the 2D package equivalent.

While the package proposed in this RFC will **not** match the implementations found in the above packages, those packages should provide a conceptual idea of what is desired. Do **not** simply copy-paste the code found in those packages.

### Notes

- If you are interested in contributing a PR which addresses this RFC and are a **first-time contributor** or not yet familiar with our project conventions, please do **not** submit LLM-generated code. Please consult our [contributing guidelines](https://github.com/stdlib-js/stdlib/blob/develop/CONTRIBUTING.md) and the associated [development guide](https://github.com/stdlib-js/stdlib/blob/develop/docs/development.md). Failure to respect project conventions will result in your PR being rejected without review. Thank you for understanding!

### Checklist

- [X] I have read and understood the [Code of Conduct](https://github.com/stdlib-js/stdlib/blob/develop/CODE_OF_CONDUCT.md).
- [X] Searched for existing issues and pull requests.
- [X] The issue name begins with `[RFC]:`.