As discussed there: sindresorhus/ky#254 (comment)

Option should allow to pass a user-function that will perform JSON parsing.

Use cases:

1. Use bourne to mitigate the hyped prototype pollution.
2. Parse JSON with reviver

Example API:

type ParseJsonFunction = <OUTPUT = unknown>(text: string) => OUTPUT

const myGot = got.extend({
  parseJson: text => bourne(text),
})

Should be available both via .extend() and as an option to each request.