Jest v28 support?

[karlhorky]

Hi @ikatyang ! 👋 Hope that you are well.

Would you be willing to support Jest v28? It seems like there were some changes around process / processAsync, which cause dts-jest to fail:

FAIL dts src/__tests__/dts-jest/003-literals-unions.test.ts
  ● Test suite failed to run

    ● Invalid return value:
      `process()` or/and `processAsync()` method of code transformer found at 
      "/home/runner/work/courses/courses/slide-decks/slideDecks/typescript-fundamentals/packages/typescript-fundamentals-exercises/node_modules/dts-jest/transform.js" 
      should return an object or a Promise resolving to an object. The object 
      must have `code` property with a string of processed code.
      This error may be caused by a breaking change in Jest 28:
      https://jestjs.io/docs/upgrading-to-jest28#transformer
      Code Transformation Documentation:
      https://jestjs.io/docs/code-transformation

      at ScriptTransformer._buildTransformResult (node_modules/@jest/transform/build/ScriptTransformer.js:507:15)
      at ScriptTransformer.transformSource (node_modules/@jest/transform/build/ScriptTransformer.js:628:17)
      at ScriptTransformer._transformAndBuildScript (node_modules/@jest/transform/build/ScriptTransformer.js:765:40)
      at ScriptTransformer.transform (node_modules/@jest/transform/build/ScriptTransformer.js:822:[19])

Test Suites: 1 failed, 4 passed, 5 total
Tests:       5 passed, 5 total
Snapshots:   0 total
Ran all test suites matching /003/i in 4 projects.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

It seems like ts-jest also did a similar upgrade here: kulshekhar/ts-jest#3490

[karlhorky]

@ikatyang Opened a PR at #410, hope this is the only relevant change from the v27 -> v28 upgrade guide.

[karlhorky]

Thanks for this @ikatyang !! Upgraded to dts-jest@25.0.0 now and it works with jest@28! 🎉