Add Support for Dynamic Library Product in Swift Package

Description

Currently, SkeletonView only provides a static library product in its Swift Package Manager configuration.
This limits flexibility for projects that require or prefer dynamic linking,
causing duplicated symbols warnings.

Problem Statement

Dynamic linking offers several benefits in certain scenarios:

• Reduced binary size when the same framework is shared across multiple app targets or extensions
• Required for certain use cases such as some app extension configurations
• Runtime flexibility for plugin architectures or modular app designs
• Faster incremental builds during development in some project setups

Proposed Solution

Add a new library product SkeletonView-Dynamic with explicit type: .dynamic to the Package.swift configuration,
while maintaining the existing static library product for backward compatibility for those who do not require it.

This would involve adding a new product entry in Package.swift:

.library(
    name: "SkeletonView-Dynamic",
    type: .dynamic,
    targets: ["SkeletonView"]
)

Benefits

• ✅ No breaking changes - existing integrations continue to work unchanged
• ✅ Provides flexibility for consumers to choose linking type based on their needs
• ✅ Follows standard Swift Package Manager practices
• ✅ Minimal maintenance overhead - uses the same target as the static library

Usage Example

After implementation, users could opt into dynamic linking:

dependencies: [
    .package(url: "https://github.com/Juanpe/SkeletonView.git", from: "1.0.0")
],
targets: [
    .target(
        name: "MyApp",
        dependencies: [
            .product(name: "SkeletonView-Dynamic", package: "SkeletonView")
        ]
    )
]

Start in Package.swift and review the existing SkeletonView library product configuration. Add the requested dynamic product while preserving the current static product, then validate that the Swift package still resolves and builds with both products available.