ultra-short, illustrative story for patterns

Story provides a more narrative, less academic description to a pattern. When a pattern has a good narrative description at the first few sections, it helps people deciding quickly whether this is something they want to dive deeper. Some patterns provide good narrative while some other patterns lack those narrative angle. It would help to add story or improve narrative description to the patterns that don't have good narratives.

Issue 中没有指定文件或测试。检查 repository 的 pattern 文档，并找出开头部分缺少简洁叙述的条目；当所选 pattern 具有有用的故事、能够帮助读者决定是否进一步探索时，即视为完成。