types: quantileSeq expands types unnecessarily

[domdomegg]

Describe the bug

The types for quantileSeq have an overly wide return type.

To Reproduce

// Type 'number | BigNumber | Unit | MathArray' is not assignable to type 'number'.
//   Type 'BigNumber' is not assignable to type 'number'.ts(2322)
const value: number = math.quantileSeq([1, 2, 3], 0.90);

I think value here should always be a number. This is the behaviour of for example math.mean and math.median.

[josdejong]

Thanks for your input, we could indeed improve the TypeScript definitions I think. Help would be welcome.