Allow FormikErrors values to be type "any" for, i18n support

[agwells]

🐛 Bug report

It looks like at one point, the FormikErrors type allowed errors to be type any, which was added in bug #266, to support i18n frameworks. But over the course of a couple of TypeScript upgrades, this got dropped, and the type was changed to string. I'd like to change it back to any, to once again make it easier to use with i18n frameworks (or just to put other React elements in error messages).

Current Behavior

When I try to return a React element as an error in a Formik validate() method, I receive a TypeScript error, saying that it must be a string:

[ts] Type 'Element' is not assignable to type 'string'. [2322]
error.tsx(6, 3): The expected type comes from property 'name' which is declared here on type 'FormikErrors<Values>'

Expected behavior

The code should compile successfully, with the supplied React element assigned to formik.errors.name.

Reproducible example

import React from 'react';
import {FormikErrors} from 'formik';
import {Trans} from '@lingui/macro';

type Values = {
  name: string
}

function validate(values: Values): FormikErrors<Values> {
  return {
    name: <Trans>error</Trans>;
  }
}

Suggested solution(s)

It looks like it's an easy fix by changing the type in types.tsx from string to any.

Your environment

Software	Version(s)
Formik	1.4.2
React	16.7.0
TypeScript	3.2.2
Browser	n/a
npm/Yarn	6.7.0
Operating System	Ubuntu 16.04