Add Italian translations for composite component

[sibest19]

This pull request adds the Italian translation file for the Composite integration. The file provides localized strings for configuration steps, options, entity states and attributes, error messages, and services, improving usability for Italian-speaking users.

Localization additions:

• Added it.json with Italian translations for all configuration steps, options, and error messages in the Composite integration, including detailed descriptions and field labels.
• Provided Italian translations for entity states and attributes for both device_tracker and sensor entities.
• Included Italian descriptions for service actions such as reloading the integration from YAML.

[pnbruckner]

@sibest19 thank you!!

With the 4.0.0 release there was one more option added for "show_unknown_as_0" (in both config.step.options.data & options.step.options.data.) If you wouldn't mind, could you add the Italian translation for it via another PR?