docs: fix a link to example (#286)

Author: thymikee

docs/GettingStarted.md

@@ -44,7 +44,7 @@ test('form submits two answers', () => {
 });
 ```
 
-You can find the source of `QuestionsBoard` component and this example [here](../src/__tests__/questionsBoard.test.js).
+You can find the source of `QuestionsBoard` component and this example [here](https://github.com/callstack/react-native-testing-library/blob/master/src/__tests__/questionsBoard.test.js).
 
 ## Installation