Documetation Update - Add detailed cloud sync branch merge process

### Code of Conduct

- [x] I have read and agree to the Insomnia Docs project's [Code of Conduct](https://github.com/Kong/insomnia-docs/blob/main/CODE_OF_CONDUCT.md).

### What article on docs.insomnia.rest is affected?

Cloud Sync --> https://docs.insomnia.rest/insomnia/insomnia-sync

### What part(s) of the article would you like to see updated?

Add a clear step-by-step guide on how to properly merge changes from a feature or dev branch (e.g., test) into the master branch using the cloud sync feature. This should include:
1. Creating and committing changes in a new branch
2. Switching back to the master branch before initiating a merge
3. Using the Merge button next to the feature branch to sync changes

### Additional information

_No response_

### Code of Conduct and Community Expectations

- [x] I agree to follow this project's Code of Conduct
- [x] I agree to abide by the Community Expectations

Open the Cloud Sync article at docs.insomnia.rest/insomnia/insomnia-sync and review its existing branch guidance. Add a step-by-step explanation covering creation and commits on a feature or dev branch, switching to master, and using the Merge button; the article should clearly describe the complete merge process.

Written by the indexing model from the issue text.