docs: add example of testing React Navigation

[cross19xx]

Summary

This PR includes

• setup an example of testing React Navigation navigator with default screen
• integration with the website

Part of #280

[thymikee]

Looks like a good start! We can't merge it without an actual example just yet

[thymikee]

This looks like a good base 👍. What users usually need is to render a specific screen, so we should add that as a followup :)

[thymikee]

We'll also need to set up running tests for examples, let's do it in a followup