fix(Object): fix _pick and _omit return type

[mrnagydavid]

In this PR, I have modified the return type of _pick and _omit to use Pick<K, T> and Omit<K, T> respectively.

[mrnagydavid]

Without better understanding of the repo, this feels hacky.

TS was complaining that retry3xx is optional in FetcherOptions and mandatory in FetcherRequest
This ? solves the complaint, but probably all the other fields should match. We should probably fix the rest, but I am afraid of a rabbit's hole.

interface FetcherRequest
  extends Omit<FetcherOptions, 'method' | 'headers' | 'baseUrl' | 'url'>  {
  retry3xx: boolean
  // ...

export interface FetcherOptions {
  retry3xx?: boolean
  // ...
}
}

[mrnagydavid]

Closing in favor of peace of mind.