docs(docs): add 236 Lowest Common Ancestor of a Binary Tree documentation

apps/docs/content/(tree)/236-lowest-common-ancestor-of-a-binary-tree.mdx

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+---
+title: '236. Lowest Common Ancestor of a Binary Tree'
+description: Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree
+sidebar:
+  label: 'Lowest Common Ancestor of a Binary Tree'
+  badge: 'Medium'
+---
+
+<Badge variant="accent">Tree DFS</Badge>
+
+### Example 1:
+- Input: `root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1`
+- Output: `3`
+- Explanation: The LCA of nodes `5` and `1` is `3`.
+
+### Example 2:
+- Input: `root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4`
+- Output: `5`
+- Explanation: The LCA of nodes `5` and `4` is `5`, since a node can be a descendant of itself according to the LCA definition.
+
+### Example 3:
+- Input: `root = [1,2], p = 1, q = 2`
+- Output: `1`
+
+### Constraints:
+
+- The number of nodes in the tree is in the range [2, 10^5].
+- `-10^9 <= Node.val <= 10^9`
+- All Node.val are unique.
+- `p != q`
+- p and q will exist in the tree.
+
+## Solution
+
+```py
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+
+class Solution:
+    def lowestCommonAncestor(
+        self, root: "TreeNode", p: "TreeNode", q: "TreeNode"
+    ) -> "TreeNode":
+
+        if not root:
+            return None
+
+        if root == p or root == q:
+            return root
+
+        l = self.lowestCommonAncestor(root.left, p, q)
+        r = self.lowestCommonAncestor(root.right, p, q)
+
+        if l and r:
+            return root
+        else:
+            return l or r
+```