Add documentation for repeated flags functionality (#2316)

Resolves #2298

- Added comprehensive "Repeated Flags" section to user guide
- Documented CountVarP for SSH-style verbose flags (-v, -vv, -vvv)
- Documented StringArrayVarP for multiple value collection
- Provided complete code examples and usage patterns

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Co-authored-by: Vergis_Ron <Vergis_Ron@bah.com>
Co-authored-by: Claude <noreply@anthropic.com>