Feature request: filter that works with promises

[alexander-azizi-martin]

I often have to filter a list but may need todo an async request to determine if an item should be kept or not (e.g. checking existence of an item in a database).

Adding a new filter function similar to the already existing map function within radashi would be helpful. Something along the lines of:

export async function filter<T>(
  array: readonly T[],
  asyncFilterFunc: (item: T, index: number) => PromiseLike<boolean>,
): Promise<K[]> {
  if (!array) {
    return []
  }
  const result = []
  let index = 0
  for (const value of array) {
    const keepValue = await asyncFilterFunc(value, index++)
    if (keepValue) {
      result.push(newValue)
    }
  }
  return result
}

If this seems like it can be added to radashi, then I can open a PR with the implementation + tests.