RFC: Welch's ANOVA (unequal variances)

## Checklist

- [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

> Sorry about a previous RFC for something that did exist in stdlib. I think I've done a better job here. I'm seeing ANOVA (`anova1`) but I'm not seeing a Welch's ANOVA (unequal variances). Perhaps adding this is a possibility?

For reference in R this is a `oneway.test()`

```r
oneway.test(var1~grp, var.equal=FALSE)
```

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