[Feature Request] Setting for including variables in completion without trigger `$`

Prerequisites

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Summary

I would like to request a setting to include variables on completion list without triggering $ to save my hand from typing it, I just don't like typing $.

Proposed Design

For example, when typing IsWi, $IsWindows should appear in completion list even if I didn't type leading $. And this kind of item should autocomplete the $ on confirm.

该 issue 未指定文件、测试或入口点。首先定位 PowerShell 补全的实现及其对触发字符的处理，然后确定变量补全的设置和覆盖测试应放在哪里。完成的标准是：该设置能够公开不带前导 $ 的变量，并确认变量补全会按描述插入 $。