Restore English README examples and add RAG/hierarchy/streaming/code/table/Dify snippets

[asukhodko]

Motivation

• Repair the Examples section after an accidental overwrite that removed a useful streaming example and introduced Russian-language text into an English README.
• Provide concrete, copy-paste examples for common pipelines such as RAG ingestion, hierarchical chunking, streaming file processing, code-context binding with adaptive sizing, table/LaTeX preservation, and Dify-compatible rendering.
• Ensure the README is consistent and immediately usable by users integrating chunkana into RAG and ingestion pipelines.

Description

• Restored and rewrote the Examples section in README.md back to English and re-added the original streaming example using MarkdownChunker.chunk_file_streaming.
• Added focused examples for RAG JSON rendering (render_json), hierarchical chunking (chunk_hierarchical / get_flat_chunks), streaming (chunk_file_streaming), code-context binding + adaptive sizing (ChunkerConfig + AdaptiveSizeConfig), tables/LaTeX preservation (preserve_latex_blocks, group_related_tables), and Dify-compatible output (render_dify_style).
• Each example now includes a short Why this matters note and an Expected output format description for clearer integration guidance.
• The only file modified is README.md (documentation-only change) with the examples consolidated and clarified.

Testing

• This is a documentation-only change and does not modify library code or runtime behavior.
• No automated tests were executed because the change only updates README.md.
• The repository test suite and CI were not affected by this change.

---

Codex Task