docs: address community issue feedback (#5 #338 #142 #246 #136 #303)

- const README: rewrite the space-saving claim per issue #5 follow-ups
  (constant-expression const vs #define immediates; which const qualify
  as constant expressions)
- const README: fix the class-section diagnosis per issue #338 (overload
  resolution picks the const overload; the restriction only surfaces
  once that overload is removed)
- sizeof README: virtual-inheritance result is compiler-dependent
  (GCC merges vbptr+vfptr -> 16, MSVC keeps them separate -> 32) #246
- static README: new section on internal linkage / access restriction
  with anonymous-namespace comparison #142
- 10-day practice: full problem list table + fixed day links #136
- new design_pattern/singleton/singleton_default.hpp: reusable
  thread-safe CRTP singleton template, compile+concurrency tested #303

basic_content/maohao/README.md

@@ -1,14 +1,15 @@
-# :: 范围解析运算符那些事
+> 本文档由 [C++那些事网站](https://light-city.github.io/stories_things/cpp-things/namespace/) 同步生成，网站版本含多语言与更新排版。
+
+# C++ 命名空间
 
 ## 关于作者：
 
 个人公众号：
 
-![](../img/wechat.jpg)
+![](https://raw.githubusercontent.com/Light-City/CPlusPlusThings/master/img/wechat.jpg)
 
 - 全局作用域符（::name）：用于类型名称（类、类成员、成员函数、变量等）前，表示作用域为全局命名空间
 - 类作用域符（class::name）：用于表示指定类型的作用域范围是具体某个类的
 - 命名空间作用域符（namespace::name）:用于表示指定类型的作用域范围是具体某个命名空间的
 
-具体代码见：[maohao.cpp](maohao.cpp)
-
+具体代码见：[maohao.cpp](https://github.com/Light-City/CPlusPlusThings/tree/master/basic_content/maohao/maohao.cpp)