Boolean intellisense

Intellisense is great for things like typeof, so why not make it great for boolean types too!

I think adding intellisense for booleans saves a bit of typing, and it still hasn't been implemented.

Look at this:

const a = (): boolean => true;
a() === // [true, false] intellisense prompt
const b = a();

if (b === /* [true, false] intellisense prompt*/) 

I think this would be a great addition to Intellisense. Any feedback is appreciated.

issue 中没有指定文件或测试。首先在编辑器中复现布尔比较示例，并跟踪现有的 typeof 补全行为；完成的标准是布尔表达式提供 true/false 补全，并且测试覆盖所展示的两个示例。