docs: add extensions reactive upgrade node

[ajpinedam]

GitHub Issue (If applicable): closes https://github.com/unoplatform/uno.extensions/issues/2555

PR Type

What kind of change does this PR introduce?

• Documentation content changes

What is the current behavior?

What is the new behavior?

This PR adds the considerations when migrating from another version of Uno.Extension.Reactive to the latest one that will include the MVUX generated name changes.

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] Tested code with current supported SDKs
• [x] Docs have been added/updated which fit documentation template. (for bug fixes / features)
• [ ] Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• [ ] Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• [x] Contains NO breaking changes
• [ ] Updated the Release Notes
• [x] Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):