Add testing examples for zoneless

[OlegSuncrown]

Information

Since Zoneless is now stable, it would be nice to have alternative test examples (Jest, Vitest), especially for rxMethod

Documentation page

https://ngrx.io/guide/signals/signal-store/testing#rxmethod

I would be willing to submit a PR to fix this issue

• Yes
• No

[rainerhahnekamp]

Yes, we also had plans to redesign the testing section. Might be a good thing to do both at once.

[markostanimirovic]

The testing guide definitely needs an overhaul. I think we can apply the "zoneless-first" approach for the entire testing guide.

[OlegSuncrown]

Thank you for the amazing work.