feat: allow overriding result types

[soedirgo]

What kind of change does this PR introduce?

feature

What is the current behavior?

Result type for .select() cannot be overridden. Since typings for nested relations is still a WIP, we need an escape hatch so people can set the types for specific fields.

What is the new behavior?

Support overriding the types for specific fields. E.g. from the tests:

// can override result type
{
  const { data, error } = await postgrest
    .from('users')
    .select('*, messages(*)')
    .returns<{ messages: { foo: 'bar' }[] }>()
  if (error) {
    throw new Error(error.message)
  }
  expectType<{ foo: 'bar' }[]>(data[0].messages)
}

Additionally, instead of always returning unknown for all nested relations, we instead return T | T[]. This is as specific as we can get despite the ambiguity.

[github-actions[bot]]

:tada: This PR is included in version 1.1.0 :tada:

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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