Revise README.md: reorganize course README, add resource index and license

[xiaoningwang]

Motivation

• Provide a clearer, more navigable repository entry for the "数据科学导论 / Introduction of Data Science" course by reorganizing and summarizing course materials.
• Make lecture materials and PDF/Markdown links easier to find for teaching and student use.
• Standardize metadata (contact, course purpose) and include repository licensing information for redistribution.

Description

• Completely replaced and restructured README.md into themed sections including repo introduction, course goals, content structure, a resource index table, lecture summaries, usage suggestions, support, contact, and license.
• Added a resources table linking lecture Markdown and PDF files such as chap1-introduction.md and the various ch*-*.pdf slides for quick access.
• Reformatted lecture-by-lecture entries (lectures 1–14) with concise learning points and unified file references.
• Appended a MIT License note and cleaned up contact information formatting for consistency.

Testing

• No automated tests are configured for documentation files in this repository, so no automated tests were run.

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Codex Task