[RFC]: add support for computing the derivative of cardinal sine (cosc)

## 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 derivative of [cardinal sine](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/math/base/special/sinc). Apart from special cases, the implementation is straightforward:

```javascript
return (cospi( x ) - (sinpi( x )/(PI*x)) / x;
```

Package: `@stdlib/math/base/special/cosc`
Alias: `base.cosc`

## Related Issues

> Does this feature request have any related issues?

No.

## 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.

Reference implementations:

- [Julia](https://github.com/JuliaLang/julia/blob/dee7d77c199c4776cf4e06afb7ce920f09ad3c8c/base/special/trig.jl#L952)

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

Start with the existing cardinal sine implementation under lib/node_modules/@stdlib/math/base/special/sinc and compare its conventions with the Julia reference implementation linked in the RFC. Add the @stdlib/math/base/special/cosc package and ensure it computes the derivative of cardinal sine, including the special cases mentioned by the issue.

Written by the indexing model from the issue text.