Add method comment

src/object.zig

@@ -97,10 +97,15 @@ pub const Object = struct {
         c.object_setIvar(self.value, ivar, val.value);
     }
 
+    /// In MacOS SDK, the memory is managed by ARC(Automatic Reference Counting).
+    /// Therefore, it not must retain an object explictlly.
+    /// But if you'd like to keep reference of objc object in ziglang-side, it could use this method to avoid releqsing object by ARC.
     pub fn retain(self: Object) Object {
         return fromId(objc_retain(self.value));
     }
 
+    /// if you have use the retain method, you must call the release method.
+    /// Otherwise, a memory leak will occur.
     pub fn release(self: Object) void {
         objc_release(self.value);
     }