Add documentation for Wazuh Indexer Packages generation

[f-galland]

Description

This PR adds documentation for the generation of Wazuh Indexer packages.

Checks

Docs building

• [x] Compiles without warnings.

Code formatting and web optimization

• [x] Uses three spaces indentation.
• [ ] Adds or updates meta descriptions accordingly.
• [ ] Updates the redirects.js script if necessary (check this guide).

Writing style

• [x] Uses present tense, active voice, and semi-formal registry.
• [x] Uses short, simple sentences.
• [x] Uses bold for user interface elements, italics for key terms or emphasis, and code font for Bash commands, file names, REST paths, and code.