[DOCS] Update Benchmarks - Include Wikipedia-100k and Wikipedia-500k run timings

[bhavnicksm]

This pull request includes significant updates to the benchmarks/README.md file, focusing on enhancing the speed benchmarks and reorganizing the size comparison sections. The most important changes include updating benchmark results for various datasets and reformatting the document for clarity.

Updates to speed benchmarks:

• Added new benchmarks for 100K and 500K Wikipedia articles, including token chunking, sentence chunking, recursive chunking, and semantic chunking.
• Updated the Paul Graham Essays dataset benchmarks to include more detailed timing results.

Reorganization of size comparison sections:

• Moved the size comparison section to the end of the document and updated the package sizes for Chonkie, LangChain, and LlamaIndex.
• Reformatted the document to improve readability and clarity, including the addition of new headings and sections.

Additional improvements:

• Updated the "Why These Numbers Matter" section to highlight both speed and size benefits.
• Revised the introductory and concluding remarks for better alignment with the updated benchmarks and comparisons.