docs: mention `module: "ES2020"` compatibility

[agilgur5]

Summary

Update docs and check-tsconfig error message to mention module: "ES2020" compatibility

Details

• it's already been supported since eb1dd17babde0b22e9540b12e671eb56d9d6bce0, but the docs and error message were not updated to mention it

  • so add both to make sure users aren't confused
  • also re-order it to be ES2015, ES2020, then ESNext consistently, which is their module order (c.f. https://github.com/microsoft/TypeScript/issues/24082)

• modify test to account for the new error message

  • make it a bit more resilient to change by only testing a substring as well (c.f. https://jestjs.io/docs/expect#tothrowerror)