Add Flatten, ToArray and RoundRobin flows

What's Changed

• Add Flatten, ToArray and RoundRobin flows by @arielf-camacho in #7

Full Changelog: v1.5.0...v1.6.0

Data stream core components

Added

• Initial core components:
  • Sources:
    • SingleSource: Emits a single value from a function
    • SliceSource: Emits all values from a slice
  • Flows:
    • FilterFlow: Filters values based on a predicate function
    • MapFlow: Transforms values using a function with optional parallelism
    • MergeFlow: Merges multiple streams into a single output stream
    • SplitFlow: Splits a stream into two based on a predicate
    • SpreadFlow: Duplicates a stream to multiple outputs
    • PassThroughFlow: Passes values through with optional type conversion
  • Sinks:
    • ChannelSink: Writes values to a Go channel
    • WriterSink: Writes byte data to an io.Writer
• Core primitives:
  • Source[T]: Interface for data sources
  • Flow[IN, OUT]: Interface for data transformations
  • Sink[T]: Interface for data consumers
  • Inlet[T] and Outlet[T]: Base interfaces for channel communication
• Builder pattern: Fluent API for configuring all components
• Context support: All components respect Go's context for cancellation
• Error handling: Customizable error handlers for robust applications
• Type safety: Full generic support with compile-time type checking
• Concurrency: Built-in support for parallel processing where appropriate
• Resource management: Automatic channel lifecycle management
• Examples: Complete working examples for all components
• Documentation: Comprehensive documentation with usage examples
• Testing: Full test coverage for all components
• Makefile: Development tools and commands for contributors