[Alerting V2] Document the Rule Versioning UI

### Description

What: The rule versioning UI
When: The feature was merged on Aug 18, 2026 https://github.com/elastic/kibana/pull/284942
Why: This feature allows a user to see a JSON diff between different versions of a rule. They can see the what, when and who of each change and compare different versions

### Resources

This feature was implemented in https://github.com/elastic/kibana/pull/284942 (UI)

### Which deployment methods does this change impact?

Elastic On-Prem and Cloud (all)

### Feature differences

The feature is identical in all deployment methods

### What Elastic Stack release is this request related to?

9.6

### Serverless release

The week of Aug 18 2026

### Collaboration model

The documentation team will create the first draft

### Point of contact.

**Main contact:** @miguelmartin-elastic @baileycash-elastic

**Stakeholders:** RNA Project team