book: fix chapter titles and unify formatting

- C++20 (ch10) is now an established standard, so drop the stale
  'Outlook'/'展望' framing; the C++26 chapter (ch12) keeps it, since
  C++26 is the genuinely forthcoming standard.
- Simplify the C++23/C++26 titles (drop 'Introduction of'/'简介').
- Unify English chapter titles to the 'Chapter NN: Title' format
  (chapters 4-9 were missing the colon), in both frontmatter and H1.
- Update both toc.md entries to match.

Author: changkun

book/en-us/04-containers.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 04 Containers"
+title: "Chapter 04: Containers"
 type: book-en-us
 order: 4
 ---
 
-# Chapter 04 Containers
+# Chapter 04: Containers
 
 [TOC]
 

book/en-us/05-pointers.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 05 Smart Pointers and Memory Management"
+title: "Chapter 05: Smart Pointers and Memory Management"
 type: book-en-us
 order: 5
 ---
 
-# Chapter 05 Smart Pointers and Memory Management
+# Chapter 05: Smart Pointers and Memory Management
 
 [TOC]
 

book/en-us/06-regex.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 06 Regular Expression"
+title: "Chapter 06: Regular Expression"
 type: book-en-us
 order: 6
 ---
 
-# Chapter 06 Regular Expression
+# Chapter 06: Regular Expression
 
 [TOC]
 

book/en-us/07-thread.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 07 Parallelism and Concurrency"
+title: "Chapter 07: Parallelism and Concurrency"
 type: book-en-us
 order: 7
 ---
 
-# Chapter 07 Parallelism and Concurrency
+# Chapter 07: Parallelism and Concurrency
 
 [TOC]
 

book/en-us/08-filesystem.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 08 File System"
+title: "Chapter 08: File System"
 type: book-en-us
 order: 8
 ---
 
-# Chapter 08 File System
+# Chapter 08: File System
 
 [TOC]
 

book/en-us/09-others.md

@@ -1,10 +1,10 @@
 ---
-title: Chapter 09 Minor Features
+title: Chapter 09: Minor Features
 type: book-en-us
 order: 9
 ---
 
-# Chapter 09 Minor Features
+# Chapter 09: Minor Features
 
 [TOC]
 

book/en-us/10-cpp20.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 10 Outlook: Introduction of C++20"
+title: "Chapter 10: C++20"
 type: book-en-us
 order: 10
 ---
 
-# Chapter 10 Outlook: Introduction of C++20
+# Chapter 10: C++20
 
 [TOC]
 

book/en-us/11-cpp23.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 11: Introduction of C++23"
+title: "Chapter 11: C++23"
 type: book-en-us
 order: 11
 ---
 
-# Chapter 11: Introduction of C++23
+# Chapter 11: C++23
 
 [TOC]
 

book/en-us/12-cpp26.md

@@ -1,10 +1,10 @@
 ---
-title: "Chapter 12: Outlook: Introduction of C++26"
+title: "Chapter 12: C++26 (Outlook)"
 type: book-en-us
 order: 12
 ---
 
-# Chapter 12: Outlook: Introduction of C++26
+# Chapter 12: C++26 (Outlook)
 
 [TOC]
 

book/en-us/toc.md

@@ -51,7 +51,7 @@
         + rvalue reference and lvalue reference
         + Move semantics
         + Perfect forwarding
-- [**Chapter 04 Containers**](./04-containers.md)
+- [**Chapter 04: Containers**](./04-containers.md)
     + 4.1 Linear containers
         + `std::array`
         + `std::forward_list`
@@ -62,12 +62,12 @@
         + basic operation
         + runtime indexing `std::variant`
         + merge and iteration
-- [**Chapter 05 Smart Pointers and Memory Management**](./05-pointers.md)
+- [**Chapter 05: Smart Pointers and Memory Management**](./05-pointers.md)
     + 5.1 RAII and reference counting
     + 5.2 `std::shared_ptr`
     + 5.3 `std::unique_ptr`
     + 5.4 `std::weak_ptr`
-- [**Chapter 06 Regular Expression**](./06-regex.md)
+- [**Chapter 06: Regular Expression**](./06-regex.md)
     + 6.1 Introduction
         + Ordinary characters
         + Special characters
@@ -76,7 +76,7 @@
         + `std::regex`
         + `std::regex_match`
         + `std::match_results`
-- [**Chapter 07 Parallelism and Concurrency**](./07-thread.md)
+- [**Chapter 07: Parallelism and Concurrency**](./07-thread.md)
     + 7.1 Basic of Parallelism
     + 7.2 Mutex and Critical Section
     + 7.3 Futures
@@ -85,23 +85,23 @@
         + Atomic Operation
         + Consistency Model
         + Memory Orders
-- [**Chapter 08 File System**](./08-filesystem.md)
+- [**Chapter 08: File System**](./08-filesystem.md)
     + 8.1 Documents and links
     + 8.2 `std::filesystem`
-- [**Chapter 09 Minor Features**](./09-others.md)
+- [**Chapter 09: Minor Features**](./09-others.md)
     + 9.1 New Types
         + `long long int`
     + 9.2 `noexcept` and Its Operations
     + 9.3 Literal
         + Raw String Literal
         + Custom String Literal
     + 9.4 Memory Alignment
-- [**Chapter 10 Outlook: Introduction of C++20**](./10-cpp20.md)
+- [**Chapter 10: C++20**](./10-cpp20.md)
     + 10.1 Concept
     + 10.2 Module
     + 10.3 Range
     + 10.4 Coroutine
-- [**Chapter 11 Introduction of C++23**](./11-cpp23.md)
+- [**Chapter 11: C++23**](./11-cpp23.md)
     + 11.1 Language features
       - Deducing this (explicit object parameter)
       - if consteval
@@ -114,7 +114,7 @@
       - std::mdspan
       - std::flat_map and std::flat_set
       - Ranges additions
-- [**Chapter 12 Outlook: Introduction of C++26**](./12-cpp26.md)
+- [**Chapter 12: C++26 (Outlook)**](./12-cpp26.md)
     + 12.1 Language features
       - Static reflection
       - Contracts