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

tool/like_python/README.md

@@ -0,0 +1,118 @@
+> 本文档由 [C++那些事网站](https://light-city.github.io/stories_things/cpp-tools/cpp-jupyter-notebook/) 同步生成，网站版本含多语言与更新排版。
+
+# C++ Jupyter Notebook 交互
+
+在Python中我们可以使用`Jupyter Notebook`直接看到结果，例如：
+
+```c
+l = [1,2]
+l
+```
+
+直接输出：
+
+```
+[1,2]
+```
+
+那当使用C++的时候，例如：
+
+```cpp
+map<string, int> mp{
+    {"one",   1},
+    {"two",   2},
+    {"three", 3},
+    {"four",  4}
+};
+```
+
+如果要输出，就得循环遍历，可否直接输出结果呢？
+
+so easy!!! `Jupyter Notebook`可以解决一切问题，哈哈～
+
+## 如何在Jupyter中玩C++？
+
+在github上有一个仓库，如下所示：
+
+> https://github.com/QuantStack/xeus-cling
+
+`xeus-cling` 是一个用于C++的Jupyter内核，基于C++解释器和Jupyter协议xeus的原生实现。
+
+目前，支持Mac与Linux，但不支持Windows。
+
+安装也是非常简单，首先安装好Anaconda，在里面创建一个虚拟环境：
+
+```
+conda create -n cling
+```
+
+切换进去：
+
+```
+conda activate cling
+```
+
+给新环境安装`jupyter`和`notebook`
+
+```
+conda install jupyter notebook
+```
+
+使用`conda-forge`安装`xeus-cling`
+
+```
+conda install xeus-cling -c conda-forge
+```
+
+为了加速安装，请记得给Anaconda配置源！
+
+检查是否安装好了内核(kernel)：
+
+```
+jupyter kernelspec list
+```
+
+输出：
+
+```cpp
+python3    /home/xxx/anaconda3/envs/cling/share/jupyter/kernels/python3
+xcpp11     /home/xxx/anaconda3/envs/cling/share/jupyter/kernels/xcpp11
+xcpp14     /home/xxx/anaconda3/envs/cling/share/jupyter/kernels/xcpp14
+xcpp17     /home/xxx/anaconda3/envs/cling/share/jupyter/kernels/xcpp17
+```
+
+打开`Jupyter Notebook`，就可以看到看到kernel了。
+
+启动`Jupyter Notebook`：
+
+```
+jupyter-notebook
+```
+
+## 如何在Jupyter中玩C？
+
+只需要安装c kernel即可！
+
+可以直接在当前环境中创建c kernel，也可以新开一个环境安装，下面是在当前环境中直接安装。
+
+```
+pip install jupyter-c-kernel
+install_c_kernel
+jupyter kernelspec list
+```
+
+此时，就输出：
+
+```cpp
+c          /home/light/anaconda3/envs/cling/share/jupyter/kernels/c
+python3    /home/light/anaconda3/envs/cling/share/jupyter/kernels/python3
+xcpp11     /home/light/anaconda3/envs/cling/share/jupyter/kernels/xcpp11
+xcpp14     /home/light/anaconda3/envs/cling/share/jupyter/kernels/xcpp14
+xcpp17     /home/light/anaconda3/envs/cling/share/jupyter/kernels/xcpp17
+```
+
+启动`Jupyter Notebook`：
+
+```
+jupyter-notebook
+```