chore: import upstream snapshot with attribution

dgl_sparse/src/matrix_ops_impl.h

@@ -0,0 +1,21 @@
+/**
+ *  Copyright (c) 2023 by Contributors
+ * @file matrix_ops_impl.h
+ * @brief DGL C++ sparse matrix operator implementations.
+ */
+#ifndef DGL_SPARSE_MATRIX_OPS_IMPL_H_
+#define DGL_SPARSE_MATRIX_OPS_IMPL_H_
+
+#include <sparse/sparse_format.h>
+#include <sparse/sparse_matrix.h>
+
+#include <tuple>
+#include <vector>
+
+#include "./utils.h"
+
+namespace dgl {
+namespace sparse {}  // namespace sparse
+}  // namespace dgl
+
+#endif  // DGL_SPARSE_MATRIX_OPS_IMPL_H_