Fix undefined: linkedliststack package issue

articles/binary-tree-diameter.md

@@ -925,6 +925,8 @@ public class Solution {
 ```
 
 ```go
+import "github.com/a234567894/gods/stacks/linkedliststack"
+
 /**
  * Definition for a binary tree node.
  * type TreeNode struct {

articles/minimum-stack.md

@@ -222,6 +222,8 @@ public class MinStack {
 ```
 
 ```go
+import "github.com/a234567894/gods/stacks/linkedliststack"
+
 type MinStack struct {
     stack *linkedliststack.Stack
 }

articles/trapping-rain-water.md

@@ -873,6 +873,8 @@ public class Solution {
 ```
 
 ```go
+import "github.com/a234567894/gods/stacks/linkedliststack"
+
 func trap(height []int) int {
     if len(height) == 0 {
         return 0

articles/validate-parentheses.md

@@ -512,6 +512,8 @@ public class Solution {
 ```
 
 ```go
+import "github.com/a234567894/gods/stacks/linkedliststack"
+
 func isValid(s string) bool {
     stack := linkedliststack.New()
     closeToOpen := map[rune]rune{')': '(', ']': '[', '}': '{'}