title: eslint throws `no-undef` errors when linting Jest test files
body: <p>I'm using Jest to write some specs and ESLint to lint the styling. </p>
  
  <p>For my <code>foo.spec.js</code> tests, eslint keeps throwing the following errors. It seems to think that <code>jest</code>, <code>beforeEach</code>, <code>afterEach</code>, etc... are not defined in that file. </p>
  
  <pre><code>   11:1   error  'beforeEach' is not defined  no-undef
     12:3   error  'jest' is not defined        no-undef
     14:13  error  'jest' is not defined        no-undef
     18:1   error  'afterEach' is not defined   no-undef
     20:1   error  'describe' is not defined    no-undef
     21:3   error  'it' is not defined          no-undef
     25:5   error  'expect' is not defined      no-undef
     28:5   error  'expect' is not defined      no-undef
     31:5   error  'expect' is not defined      no-undef
     34:3   error  'it' is not defined          no-undef
     38:5   error  'expect' is not defined      no-undef
     41:5   error  'jest' is not defined        no-undef
     42:5   error  'expect' is not defined      no-undef
     43:5   error  'expect' is not defined      no-undef
     46:3   error  'it' is not defined          no-undef
     54:5   error  'expect' is not defined      no-undef
     58:5   error  'jest' is not defined        no-undef
  </code></pre>
  
  <p>I believe those are included by jest automatically and so they don't need to be explicitly imported in my spec files. In fact the only thing I import via my <code>jest.setup.js</code> file is</p>
  
  <pre><code>import "react-testing-library/cleanup-after-each";
  import "jest-dom/extend-expect";
  </code></pre>
  
  <p>Is there a way to eliminate these errors without having to disable eslint rules at the top of each individual file or inline? </p>
  
  <p>Thanks!</p>