General-purpose utility types/type guards (maybe in a new `types` package scope)

[lionel-rowe]

Is your feature request related to a problem? Please describe.

There are various common utility types that aren't available in TypeScript's built-in libraries. For example:

export type NonEmptyArray<T> = [T, ...T[]]
export function isNonEmptyArray<T>(arr: T[]): arr is NonEmptyArray<T> {
    return arr.length > 0
}

In some cases, these can be somewhat complex, in others (like NonEmptyArray) implementation is somewhat trivial, but also involves design decisions where the tradeoffs may not be initially obvious — for example, what if anything is the practical difference between [T, ...T[]] vs T[] & { 0: T }?

Describe the solution you'd like

Maybe a new @std/types package scope? That would be the first place I'd look for this kind of thing.

The only existing examples I know of in std are ExpandRecursively under collections/deep-merge, but there may be a few more.

Describe alternatives you've considered

Include type utils distributed in various other packages, but that's likely to be less discoverable — I only stumbled upon ExpandRecursively by accident after re-implementing similar logic multiple times.