Add Sub impl

Add an implementation for the forward function of the sub operator

Note: No unit test have been added (an issue for this has been created here: #16)

include/aidge/backend/cuda/operator/SubImpl.hpp

+/********************************************************************************
+ * Copyright (c) 2023 CEA-List
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ ********************************************************************************/
+
+#ifndef AIDGE_BACKEND_CUDA_OPERATOR_SUBIMPL_H_
+#define AIDGE_BACKEND_CUDA_OPERATOR_SUBIMPL_H_
+
+#include <array>
+#include <memory>
+#include <tuple>
+#include <vector>
+
+#include <cudnn.h>
+
+#include "aidge/backend/OperatorImpl.hpp"
+#include "aidge/operator/Sub.hpp"
+#include "aidge/utils/Registrar.hpp"
+#include "aidge/utils/Types.h"
+
+#include "aidge/backend/cuda/utils/CudaUtils.hpp"
+
+namespace Aidge {
+class SubImpl_cuda : public OperatorImpl {
+private:
+
+
+public:
+    SubImpl_cuda(const Sub_Op &op) : OperatorImpl(op, "cuda") {}
+
+    static std::unique_ptr<SubImpl_cuda> create(const Sub_Op &op) {
+        return std::make_unique<SubImpl_cuda>(op);
+    }
+
+public:
+    void forward();
+    // ~SubImpl_cuda();
+private:
+    template <class T> void forward_(const std::vector<Tensor>& inputs, const std::vector<std::vector<int>>& inputsDims, const std::vector<std::vector<int>>& inputsStrides);
+};
+
+namespace {
+// add cuda backend to Sub_Op implementation registry
+static Registrar<Sub_Op> registrarSubImpl_cuda("cuda", Aidge::SubImpl_cuda::create);
+}  // namespace
+}  // namespace Aidge
+
+#endif /* AIDGE_BACKEND_CUDA_OPERATOR_SUBIMPL_H_ */