feat: Adds RenderBytesTo for rendering markdown to a externally provided writer

[maciej-sz]

Added a new RenderBytesTo function that allows rendering markdown directly to an externally provided writer. This gives users more control over the output destination, enabling various use cases such as:

• Writing directly to files without intermediate buffers
• Streaming output to network connections
• Using custom writers with additional processing logic
• Integration with existing I/O pipelines

Key changes:

• Added a new package-level RenderBytesTo function that accepts a writer
• Added a RenderBytesTo method to the TermRenderer type
• Refactored RenderBytes to use the new RenderBytesTo method
• Added comprehensive tests for the new functionality

Related issue/discussion: N/A

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• I have performed a self-review of my code

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