[Functions] Add fd tensor concat (#507)

* Add fd tensor concat

* fix comment

fastdeploy/function/concat.h

@@ -0,0 +1,30 @@
+// Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
+//
+// 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.
+
+#pragma once
+
+#include "fastdeploy/core/fd_tensor.h"
+
+namespace fastdeploy {
+
+/** Excute the concatenate operation for input FDTensor along given axis.
+    @param x The input tensor.
+    @param out The output tensor which stores the result.
+    @param axisi Axis which will be concatenated.
+*/
+
+FASTDEPLOY_DECL void Concat(const std::vector<FDTensor>& x, FDTensor* out,
+                            int axis = 0);
+
+}  // namespace fastdeploy