Feature: Adding support for custom @tags

先找出文件匯出器及其產生的 JSON 文件，接著追蹤 Lua 註解如何被解析與匯出。定義 custom_tags 項目（包括標題、隱藏旗標和格式函式）應如何表示在匯出的 JSON 中；當不需要內部使用即可解析和後處理自訂標籤時，即表示完成。

One of the nice things with LDoc was the ability to define custom tags, so they could be used to give additional annotations.

As an example, this is the tags section of one of our projects.

custom_tags = {
	{"baseclass", title = "BaseClass", hidden = true},
	{"state", title = "State", hidden = true},

	{"warns", title = "Warnings", format = function(...)
		return "<span class='tag-warning'>" .. markup(...) .. "</span>"
	end},
	{"bugs", title = "Known Issues", format = function(...)
		return "<span class='tag-bugs'>" .. markup(...) .. "</span>"
	end},
	{"deprecated", title = "Deprecated", format = function(str)
		if str == "" then
			return "<span class='tag-deprecated'>This function is deprecated and may be removed in a future version.</span>"
		else
			return "<span class='tag-deprecated'>This function is deprecated and may be removed in a future version.<br>" .. markup(str) .. "</span>"
		end
	end},
	{"internal", title = "Internal", format = function(str)
		if str == "" then
			return "<span class='tag-internal'>This function is internal. Whilst you can call it, you probably shouldn't.</span>"
		else
			return "<span class='tag-internal'>This function is internal. Whilst you can call it, you probably shouldn't.<br>" .. markup(str) .. "</span>"
		end
	end}
}

Even if these aren't used internally, being able to define them for LuaLS to parse and export from the docs exporter in the json document would allow us to do post-processing on the files.