Fix minor error in documents

[Javgilavi]

Description

I discovered an enumeration error in the README.md while reading the document for my first days in the company. Also inside FAST DDS -> 3.1.2.2.1 -> Example the XML was change to support all possibilities available. Also inside FAST DDS -> 12.1.8 -> Fix error on XML code. This PR fixes them.

Contributor Checklist

• [ ] Commit messages follow the project guidelines.
• N/A Code snippets related to the added documentation have been provided.
• [x] Documentation tests pass locally.
• [ ] Applicable backports have been included in the description.

Reviewer Checklist

• [ ] The PR has a milestone assigned.
• [ ] The title and description correctly express the PR's purpose.
• [ ] Check contributor checklist is correct.
• [ ] CI passes without warnings or errors.