Feature: Adding support for custom @tags

首先定位文档导出器及其生成的 JSON 文档，然后追踪 Lua 注解的解析和导出方式。定义 custom_tags 条目（包括标题、隐藏标志和格式化函数）应如何表示在导出的 JSON 中；当无需内部使用即可解析和后处理自定义标签时，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.