Bug fixes and improvements (#1572)

* Sync zh and zh-hant versions.

* Remove the polyfill.io link from mkdocs.yml

* Update contributors' info for code reviewers and en/zh-hant versions reviewers.

* Fix graph.md

* Update avatars for English version reviewers.

* Sync zh and zh-hant versions.

* Fix two_sum_brute_force.png

* Sync zh and zh-hant versions.
Optimize structrue of index.html.

* Format index.html

zh-hant/codes/rust/chapter_backtracking/preorder_traversal_i_compact.rs

@@ -4,10 +4,8 @@
  * Author: codingonion (coderonion@gmail.com)
  */
 
-include!("../include/include.rs");
-
+use hello_algo_rust::include::{print_util, vec_to_tree, TreeNode};
 use std::{cell::RefCell, rc::Rc};
-use tree_node::{vec_to_tree, TreeNode};
 
 /* 前序走訪：例題一 */
 fn pre_order(res: &mut Vec<Rc<RefCell<TreeNode>>>, root: Option<&Rc<RefCell<TreeNode>>>) {

zh-hant/codes/rust/chapter_backtracking/preorder_traversal_ii_compact.rs

@@ -4,10 +4,8 @@
  * Author: codingonion (coderonion@gmail.com)
  */
 
-include!("../include/include.rs");
-
+use hello_algo_rust::include::{print_util, vec_to_tree, TreeNode};
 use std::{cell::RefCell, rc::Rc};
-use tree_node::{vec_to_tree, TreeNode};
 
 /* 前序走訪：例題二 */
 fn pre_order(

zh-hant/codes/rust/chapter_backtracking/preorder_traversal_iii_compact.rs

@@ -4,10 +4,8 @@
  * Author: codingonion (coderonion@gmail.com)
  */
 
-include!("../include/include.rs");
-
+use hello_algo_rust::include::{print_util, vec_to_tree, TreeNode};
 use std::{cell::RefCell, rc::Rc};
-use tree_node::{vec_to_tree, TreeNode};
 
 /* 前序走訪：例題三 */
 fn pre_order(

zh-hant/codes/rust/chapter_backtracking/preorder_traversal_iii_template.rs

@@ -4,10 +4,8 @@
  * Author: codingonion (coderonion@gmail.com)
  */
 
-include!("../include/include.rs");
-
+use hello_algo_rust::include::{print_util, vec_to_tree, TreeNode};
 use std::{cell::RefCell, rc::Rc};
-use tree_node::{vec_to_tree, TreeNode};
 
 /* 判斷當前狀態是否為解 */
 fn is_solution(state: &mut Vec<Rc<RefCell<TreeNode>>>) -> bool {