[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

首先找出 completion.requireSeparator 設定的實作，以及語言伺服器現有的診斷處理。使用設定為 / 並以 . 呼叫 require 的範例進行重現，然後將完成條件定義為：回報不正確的分隔符號，並在使用已設定的分隔符號時不發出警告。