[Feature Request] Diagnostic for using wrong require separator

The setting completion.requireSeparator allows the user to define a certain character to use as the separator when require-ing a file. It would be nice to have a diagnostic that warns the user if he violates this setting.

Example

"Lua.completion.requireSeparator": {
                    "default": "/"
}

local strings = require("helpers.strings")
                               ^^^  --Warning: Wrong separator

首先定位 completion.requireSeparator 设置的实现，以及语言服务器现有的诊断处理。使用配置为 / 的设置和使用 . 的 require 调用重现该示例，然后将完成条件定义为：报告错误的分隔符，但在使用已配置的分隔符时不发出警告。