Add documentation for the ISM rollover policy

[AlexRuiz7]

Description

This PR adds documentation about the ISM rollover policy added to the product.

Closes #6683

Checks

Docs building

• Compiles without warnings.

Code formatting and web optimization

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

Writing style

• 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.

[AlexRuiz7]

LGTM!