Add missing file

Signed-off-by: Addisu Z. Taddese <[email protected]>

include/gz/sim/Constants.hh

@@ -0,0 +1,39 @@
+/*
+ * Copyright (C) 2024 Open Source Robotics Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GZ_SIM_CONSTANTS_HH_
+#define GZ_SIM_CONSTANTS_HH_
+
+#include "gz/sim/config.hh"
+#include <string_view>
+
+namespace gz::sim
+{
+// Inline bracket to help doxygen filtering.
+inline namespace GZ_SIM_VERSION_NAMESPACE
+{
+  namespace  config_action {
+    constexpr std::string_view kPluginAttribute{"gz:config_action"};
+    constexpr std::string_view kPrependReplace{"prepend_replace"};
+    constexpr std::string_view kPrepend{"prepend"};
+    constexpr std::string_view kAppendReplace{"append_replace"};
+    constexpr std::string_view kAppend{"append"};
+  }
+}
+}  // namespace gz::sim
+
+#endif