translation: Capitalize all the headers, list headers and figure captions (#1206)

* Capitalize all the headers, list headers and figure captions

* Fix the term "LRU"

* Fix the names of source code link in avl_tree.md

* Capitalize only first letter for nav trees in mkdocs.yml

* Update code comments

* Update linked_list.md

* Update linked_list.md

en/docs/chapter_stack_and_queue/stack.md

@@ -6,13 +6,13 @@ We can compare a stack to a pile of plates on a table. To access the bottom plat
 
 As shown in the figure below, we refer to the top of the pile of elements as the "top of the stack" and the bottom as the "bottom of the stack." The operation of adding elements to the top of the stack is called "push," and the operation of removing the top element is called "pop."
 
-![Stack's Last-In-First-Out Rule](stack.assets/stack_operations.png)
+![Stack's last-in-first-out rule](stack.assets/stack_operations.png)
 
-## Common Operations on Stack
+## Common operations on stack
 
 The common operations on a stack are shown in the table below. The specific method names depend on the programming language used. Here, we use `push()`, `pop()`, and `peek()` as examples.
 
-<p align="center"> Table <id> &nbsp; Efficiency of Stack Operations </p>
+<p align="center"> Table <id> &nbsp; Efficiency of stack operations </p>
 
 | Method   | Description                                     | Time Complexity |
 | -------- | ----------------------------------------------- | --------------- |
@@ -312,13 +312,13 @@ Typically, we can directly use the stack class built into the programming langua
 
     https://pythontutor.com/render.html#code=%22%22%22Driver%20Code%22%22%22%0Aif%20__name__%20%3D%3D%20%22__main__%22%3A%0A%20%20%20%20%23%20%E5%88%9D%E5%A7%8B%E5%8C%96%E6%A0%88%0A%20%20%20%20%23%20Python%20%E6%B2%A1%E6%9C%89%E5%86%85%E7%BD%AE%E7%9A%84%E6%A0%88%E7%B1%BB%EF%BC%8C%E5%8F%AF%E4%BB%A5%E6%8A%8A%20list%20%E5%BD%93%E4%BD%9C%E6%A0%88%E6%9D%A5%E4%BD%BF%E7%94%A8%0A%20%20%20%20stack%20%3D%20%5B%5D%0A%0A%20%20%20%20%23%20%E5%85%83%E7%B4%A0%E5%85%A5%E6%A0%88%0A%20%20%20%20stack.append%281%29%0A%20%20%20%20stack.append%283%29%0A%20%20%20%20stack.append%282%29%0A%20%20%20%20stack.append%285%29%0A%20%20%20%20stack.append%284%29%0A%20%20%20%20print%28%22%E6%A0%88%20stack%20%3D%22,%20stack%29%0A%0A%20%20%20%20%23%20%E8%AE%BF%E9%97%AE%E6%A0%88%E9%A1%B6%E5%85%83%E7%B4%A0%0A%20%20%20%20peek%20%3D%20stack%5B-1%5D%0A%20%20%20%20print%28%22%E6%A0%88%E9%A1%B6%E5%85%83%E7%B4%A0%20peek%20%3D%22,%20peek%29%0A%0A%20%20%20%20%23%20%E5%85%83%E7%B4%A0%E5%87%BA%E6%A0%88%0A%20%20%20%20pop%20%3D%20stack.pop%28%29%0A%20%20%20%20print%28%22%E5%87%BA%E6%A0%88%E5%85%83%E7%B4%A0%20pop%20%3D%22,%20pop%29%0A%20%20%20%20print%28%22%E5%87%BA%E6%A0%88%E5%90%8E%20stack%20%3D%22,%20stack%29%0A%0A%20%20%20%20%23%20%E8%8E%B7%E5%8F%96%E6%A0%88%E7%9A%84%E9%95%BF%E5%BA%A6%0A%20%20%20%20size%20%3D%20len%28stack%29%0A%20%20%20%20print%28%22%E6%A0%88%E7%9A%84%E9%95%BF%E5%BA%A6%20size%20%3D%22,%20size%29%0A%0A%20%20%20%20%23%20%E5%88%A4%E6%96%AD%E6%98%AF%E5%90%A6%E4%B8%BA%E7%A9%BA%0A%20%20%20%20is_empty%20%3D%20len%28stack%29%20%3D%3D%200%0A%20%20%20%20print%28%22%E6%A0%88%E6%98%AF%E5%90%A6%E4%B8%BA%E7%A9%BA%20%3D%22,%20is_empty%29&cumulative=false&curInstr=2&heapPrimitives=nevernest&mode=display&origin=opt-frontend.js&py=311&rawInputLstJSON=%5B%5D&textReferences=false
 
-## Implementing a Stack
+## Implementing a stack
 
 To gain a deeper understanding of how a stack operates, let's try implementing a stack class ourselves.
 
 A stack follows the principle of Last-In-First-Out, which means we can only add or remove elements at the top of the stack. However, both arrays and linked lists allow adding and removing elements at any position, **therefore a stack can be seen as a restricted array or linked list**. In other words, we can "shield" certain irrelevant operations of an array or linked list, aligning their external behavior with the characteristics of a stack.
 
-### Implementation Based on Linked List
+### Implementation based on a linked list
 
 When implementing a stack using a linked list, we can consider the head node of the list as the top of the stack and the tail node as the bottom of the stack.
 
@@ -339,7 +339,7 @@ Below is an example code for implementing a stack based on a linked list:
 [file]{linkedlist_stack}-[class]{linked_list_stack}-[func]{}
 ```
 
-### Implementation Based on Array
+### Implementation based on an array
 
 When implementing a stack using an array, we can consider the end of the array as the top of the stack. As shown in the figure below, push and pop operations correspond to adding and removing elements at the end of the array, respectively, both with a time complexity of $O(1)$.
 
@@ -358,7 +358,7 @@ Since the elements to be pushed onto the stack may continuously increase, we can
 [file]{array_stack}-[class]{array_stack}-[func]{}
 ```
 
-## Comparison of the Two Implementations
+## Comparison of the two implementations
 
 **Supported Operations**
 
@@ -383,7 +383,7 @@ However, since linked list nodes require extra space for storing pointers, **the
 
 In summary, we cannot simply determine which implementation is more memory-efficient. It requires analysis based on specific circumstances.
 
-## Typical Applications of Stack
+## Typical applications of stack
 
 - **Back and forward in browsers, undo and redo in software**. Every time we open a new webpage, the browser pushes the previous page onto the stack, allowing us to go back to the previous page through the back operation, which is essentially a pop operation. To support both back and forward, two stacks are needed to work together.
 - **Memory management in programs**. Each time a function is called, the system adds a stack frame at the top of the stack to record the function's context information. In recursive functions, the downward recursion phase keeps pushing onto the stack, while the upward backtracking phase keeps popping from the stack.