Introduce the .readonly() method

[aryaemami59]

This PR:

• Introduces the .readonly() method for transforming object properties to readonly.

Details:

.readonly() works similarly to the native Readonly utility type.

Default Behavior:

When no arguments are passed to .readonly(), it behaves like the Readonly utility, converting all properties of the target type to readonly. For example:

import { expectTypeOf } from 'expect-type'

type Post = {
  title: string
  content: string
}

expectTypeOf<Post>().readonly().toEqualTypeOf<Readonly<Post>>()

Selective Readonly Properties:

You can also specify particular properties to make readonly by passing the keys of the target object as parameters. Only those specified properties will become readonly while others remain mutable. For instance:

import { expectTypeOf } from 'expect-type'

type Post = {
  title: string
  content: string
}

expectTypeOf<Post>()
  .readonly('title')
  .toEqualTypeOf<{ readonly title: string; content: string }>()

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pnpm add https://pkg.pr.new/mmkal/expect-type@117

commit: 2b28aab