[Add] Load/Save angle velocity.

src/dynamic_body.cpp

@@ -16,11 +16,13 @@ DynamicBody::DynamicBody(void) : ModelBody() {
 void DynamicBody::Save(void) {
   using namespace Serializer::Write;
   ModelBody::Save();
+  wr_vector3d(GetAngVelocity());
 }
 
 void DynamicBody::Load(void) {
   using namespace Serializer::Read;
   ModelBody::Load();
+  SetAngVelocity(rd_vector3d());
 }
 
 void DynamicBody::Enable(void) {