Expanded skill to support all major Withings health metrics and improved documentation.

• Added support for retrieving body composition, activity, and sleep data in addition to weight.
• Expanded documentation on when and how to use the skill, with detailed command examples and sample outputs.
• Clarified error handling and troubleshooting steps.
• Updated description to reflect broader capabilities (not just weight/activity).
• Documented data formats and new command options for body metrics, activity period, and sleep history.