Module 4 (datastructures) it too front-loaded on information

The module on datastructures suffers from a few issues:
- All the information is at the beginning, with exercises at the end
- The module is "hard" for day 1
- The module is often taught at the end of day 1, with concetration waning

These issues make the information bit too long and hard to follow. I propose exercises between the different sections. Logical points:

- After basic lists and indexing
- After slicing, `in`, `len`
- After tuples

找到 Module 4 datastructures 教材，並檢視其中現有的章節與練習。在基本列表和索引之後、slicing、`in` 和 `len` 之後，以及 tuple 之後插入練習；當資訊在這些教學節點分開時，即表示完成。

由索引模型根據 Issue 內容生成。