Add Python code (Chapter of searching)

to the docs.

docs/chapter_searching/linear_search.md

@@ -47,7 +47,13 @@ comments: true
 === "Python"
 
     ```python title="linear_search.py"
-
+    """ 线性查找（数组） """
+    def linear_search(nums, target):
+        # 遍历数组
+        for i in range(len(nums)):
+            if nums[i] == target:  # 找到目标元素，返回其索引
+                return i
+        return -1                  # 未找到目标元素，返回 -1
     ```
 
 === "Go"
@@ -119,7 +125,14 @@ comments: true
 === "Python"
 
     ```python title="linear_search.py"
-
+    """ 线性查找（链表） """
+    def linear_search1(head, target):
+        # 遍历链表
+        while head:
+            if head.val == target: # 找到目标结点，返回之
+                return head
+            head = head.next
+        return None                # 未找到目标结点，返回 None
     ```
 
 === "Go"