Consider to clarify "use strict" concept

还没有人认领这个 Issue。

Hello

About "use strict" in https://javascript.info/strict-mode is indicated:

> This was the case until 2009 when ECMAScript 5 (ES5) appeared. It added new features to the language and modified some of the existing ones. _To keep the old code working, most such modifications are off by default. You need to explicitly enable them with a special directive: "use strict"_

The italic part is not very clear (I read the spanish version too), it gives the idea that "use strict" enables the old mode code

Of course in https://javascript.info/javascript-specials#strict-mode is more clear with:

> _To fully enable all features of **modern JavaScript**, we should start scripts with "use strict"._

Thank you

从 javascript.info/strict-mode 和 javascript.info/javascript-specials#strict-mode 中关于严格模式的部分开始，并比较其中引用的解释。明确斜体句子的含义，使其不会暗示 "use strict" 会启用遗留行为；当解释与更清晰的措辞一致并消除歧义时，即可视为完成。

由索引模型根据 Issue 内容生成。