[RFC]: Add `@stdlib/random/array/randn`

### Description

This RFC proposes adding support for creating an array of normally distributed pseudorandom numbers with the option to select the underlying PRNG. This is the array creation analog of `@stdlib/random/base/randn`.

Package: `@stdlib/random/array/randn`
Alias: `randn`

### Related Issues

None.

### Questions

No.

### Other

- A package with a similar implementation/API design is [`@stdlib/random/array/randu`](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/random/array/randu).

### 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:`.

Start by comparing the proposed package with lib/node_modules/@stdlib/random/array/randu and the analogous @stdlib/random/base/randn package. Define the array API, normal distribution behavior, and selectable PRNG support from those references; done means the new @stdlib/random/array/randn package provides that functionality consistently.

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