fix: add React.Fragment support for matching text

[Alvindelito]

Summary

This PR builds upon #663

I have used the code provided by @lachiet with an added conditional.

Searching for text by using getByText() should now detect the text inside of a <React.Fragment> nested in a <Text> component.

<Text>
  <React.Fragment>Hello world</React.Fragment>
</Text>

Test plan

I have included a test to test the new change and all other tests have passed.

[thymikee]

Thanks for your contribution @Alvindelito! Can you test if this works with nested fragments as well? Checking for parent.parent proved to be buggy in the past. Also, have you considered updating the getChildrenAsText method to check for Fragment type? We could use react-is for this.

[thymikee]

Closed via #934