Include tests

[MatthewCaseres]

I don't see tests in the project. Maybe for the example implementations (like https://elilambnz.github.io/react-py/docs/examples/custom-modules) we can have some tests written in Playwright allowing iteration on the underlying logic while maintaining confidence in the behavior of the software?

[elilambnz]

Thanks for the suggestion, I'll look into using Playwright for tests.