Add same tree constrains

Author: onixlas

binary-tree/100_Same_Tree/README.md

@@ -18,6 +18,12 @@ Output: `false`
 Input: `p = [1,2,1], q = [1,1,2]`
 Output: `false`
 
+**Constraints:**
+
+* The number of nodes in both trees is in the range `[0, 100]`.
+* `-10^4 <= Node.val <= 10^4`
+
+
 ## Solution
 
 ```python