docs(svelte): Adds setup information for testing-library-svelte

docs/svelte-testing-library/setup.md

@@ -47,25 +47,36 @@ with any testing framework and runner you're comfortable with.
  }
  ```
 
-5. This is optional but it is recommended, you can install
+5. If you are using ES6 modules in your project you have to add Jest's babel
+ transform setting (it is set by default, but since we are overriding the
+ transform config, we have to add it explicitly)
+
+ ```json
+ "transform": {
+ "^.+\\.js$": "babel-jest",
+ "^.+\\.svelte$": "svelte-jester"
+ },
+ ```
+
+6. This is optional but it is recommended, you can install
  [jest-dom](https://github.com/testing-library/jest-dom) to add handy
  assertions to Jest
 
- 5.1 Install jest-dom
+ 6.1 Install jest-dom
 
  ```
  npm install --save-dev @testing-library/jest-dom
  ```
 
- 5.2 Add the following to your Jest configuration in `package.json`
+ 6.2 Add the following to your Jest configuration in `package.json`
 
  ```json
  {
  "setupFilesAfterEnv": ["@testing-library/jest-dom/extend-expect"]
  }
  ```
 
-6. Create your component + test file (checkout the rest of the docs to see how)
+7. Create your component + test file (checkout the rest of the docs to see how)
  and run it
 
  ```