对 Item2 的建议：标注 auto x4{27} 语义已经变化

[Patricky-Tau]

auto x4{27} 在书中称 auto 推导出 std::initializer_list<int>。然而，在 N3922 之后，将会推导出 int。

auto x1 = {3}; // x1 is std::initializer_list<int>
auto x2{1, 2}; // error: not a single element
auto x3{3};    // x3 is int
               // (before N3922 x2 and x3 were both std::initializer_list<int>)

-- cppreference

在作者的网站中也指出了这一点：

有许多同学用这本书入门，建议标注出这一点。

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参考资料：

• https://www.aristeia.com/BookErrata/emc++-errata.html
• https://en.cppreference.com/w/cpp/language/template_argument_deduction#auto_type_deduction
• https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3922.html

[wendajiang]

It's look like that you have fixed on your own repo, it's pleasure to submit the PR :)