Add Maltiverse integration section

[fdalmaup]

Description

Closes #6216. It adds the Maltiverse native integration section in the Integration with external APIs page of the documentation and the corresponding integration reference.

Checks

• Compiles without warnings.
• Uses present tense, active voice, and semi-formal registry.
• Uses short, simple sentences.
• Uses bold for user interface elements, italics for key terms or emphasis, and code font for Bash commands, file names, REST paths, and code.
• Uses three spaces indentation.
• Adds or updates meta descriptions accordingly.
• Updates the redirects.js script if necessary (check this guide).

[GGP1]

The instructions, syntax and spelling is correct, the links are pointed to the right resources and the styling of the content matches the rest of the content

LGTM

[javimed]

LGTM