refactor(ch1-4): align filenames and update corresponding README sections

m04_langchain_basics/s02_prompt.py

@@ -0,0 +1,10 @@
+from langchain_core.prompts import ChatPromptTemplate
+
+# 定义提示词模板(推荐写法)
+prompt = ChatPromptTemplate.from_messages([
+        ("system","你非常可爱，说话末尾会带个喵"),
+        ("human","{input}") # {input}:占位符
+])
+# 格式化输出
+formatted_prompt = prompt.invoke({"input":"你好喵"})
+print(formatted_prompt)