Implement more async utils

[tshemsedinov]

type Callback = (err: Error | null, result: unknown) => void;
type AsyncFunction = (...args: unknown[]) => Promise<unknown>;

export function callbackify(fn: AsyncFunction): CallbackLast;
export function promisify(fn: CallbackLast): AsyncFunction;
export function debounce(fn: SyncFunction, delay: number): SyncFunction;
export function throttle(fn: SyncFunction, interval: number): SyncFunction;

[ArtemDmitrenko]

@tshemsedinov
May I implement these utils?

[tshemsedinov]

@ArtemDmitrenko yes, please create branch from my branch async-utils and pull request from your to async-utils, so I'll land commits to async-utils and will release on next major release

[ArtemDmitrenko]

@tshemsedinov
As I can see these utils have been already added by you here
Correct?

[tshemsedinov]

@ArtemDmitrenko This is a copy of the old code, it may be useful, but it needs some work, maybe there are inconvenient contracts, maybe the implementation can be optimized, need more tests, typings, docs, use cases...