feat: add defaults func for table merge

defaults_table.lua

@@ -0,0 +1,20 @@
+-- merge defaults value to target table
+local function defaults(target, default)
+  if not target then target = {} end
+  if not default then return target end
+  for k,v in pairs(default) do
+    local value = target[k]
+    if type(v) == "table" then
+      if type(value) ~= "table" then
+        value = {}
+        target[k] = value
+      end
+      defaults(value, v)
+    else
+      if (value == nil) then target[k] = v end
+    end
+  end
+  return target
+end
+
+return defaults