Add introduce about "useBabelrc" and ES import

[whitetrefoil]

See #265

[morajabi]

I think there's no need to repeat this code snippet again. We can reference the main one here IMO.

[morajabi]

I think it's OK.

[whitetrefoil]

Just FYI, I added the second section because this problem seems only exist when using ts-jest. Without ts-jest the project's. babelrc will be used so as long as the project can be built the tests can be run. But when ts-jest is used, the tests will fail even the code can be built, and the error message just helps nothing. This may confuse newbies.

And so sorry for my English skill, I should be more careful when writing documents since I'm not a native English speaker.

[kulshekhar]

Just FYI, I added the second section because this problem seems only exist when using ts-jest. Without ts-jest the project's. babelrc will be used so as long as the project can be built the tests can be run. But when ts-jest is used, the tests will fail even the code can be built, and the error message just helps nothing. This may confuse newbies.

The first section addresses this issue. The configuration details for .babelrc aren't specific to ts-jest. Including documentation for that here could be more confusing, for example, when something babel specific changes.

Currently, anyone who wants to use a custom .babelrc can refer to the babel documentation to see how to do it. That documentation is more likely to be more accurate over a period of time.

And so sorry for my English skill, I should be more careful when writing documents since I'm not a native English speaker.

We really appreciate all contributions so don't worry about this 😄. English isn't the first language for a lot of us so we understand!