add jest & rtl

[SergiuPintilei]

Add Jest and RTL following the official guide.

Also added 2 examples (no strong opinion about the folder structure).

https://nextjs.org/docs/testing#setting-up-jest-with-the-rust-compiler

Do we want dedicated tests folder or add them inside each component's folder?

[cleferman]

I would go with a tests folder inside each component's folder. Easier to find the tests through the folder structure and there are less files in the component's folder.

Could you also update the generate_component/index.js so it automatically adds the tests folder along with the Component.test.tsx file?

[SergiuPintilei]

I would go with a tests folder inside each component's folder. Easier to find the tests through the folder structure and there are less files in the component's folder.

Could you also update the generate_component/index.js so it automatically adds the tests folder along with the Component.test.tsx file?

done