feat: added support for plugin packages by lazy, rockspec and packspec

lua/lazy/pkg/lazy.lua

@@ -0,0 +1,28 @@
+local Util = require("lazy.util")
+
+local M = {}
+
+M.lazy_file = "lazy.lua"
+
+---@param plugin LazyPlugin
+---@return LazyPkg?
+function M.get(plugin)
+  local file = Util.norm(plugin.dir .. "/" .. M.lazy_file)
+  if Util.file_exists(file) then
+    ---@type fun(): LazySpec
+    local chunk = Util.try(function()
+      local ret, err = loadfile(file)
+      return err and error(err) or ret
+    end, "`" .. M.lazy_file .. "` for **" .. plugin.name .. "** has errors:")
+    if not chunk then
+      Util.error("Invalid `" .. M.lazy_file .. "` for **" .. plugin.name .. "**")
+    end
+    return {
+      source = "lazy",
+      file = M.lazy_file,
+      chunk = chunk,
+    }
+  end
+end
+
+return M