title: How to correctly import custom types in typescript
body: <p>I have custom type in <code>src/@types/app.d.ts</code> ( <code>export type AuthKeyT = string</code> )</p>
  
  <p>I would like to use it in <code>tsx</code> react file (using <code>import { AuthKeyT } from '@types/app'</code>), but I am getting an error:</p>
  
  <blockquote>
    <p>Cannot import type declaration files. Consider importing 'app' instead of '@types/app' </p>
  </blockquote>
  
  <p>So, when I use <code>import { AuthKeyT } from 'app'</code> I am getting:</p>
  
  <blockquote>
    <p>Cannot find module 'app'.</p>
  </blockquote>
  
  <p>So.. what is wrong? How should I import custom type?</p>
  
  <p>I am using typescript <code>3.7.2</code> in react app.</p>