Add specialized kron for sparse outer products

stdlib/SparseArrays/src/linalg.jl

@@ -1198,6 +1198,9 @@ kron(x::SparseVector, A::SparseMatrixCSC) = kron(SparseMatrixCSC(x), A)
 kron(A::Union{SparseVector,SparseMatrixCSC}, B::VecOrMat) = kron(A, sparse(B))
 kron(A::VecOrMat, B::Union{SparseVector,SparseMatrixCSC}) = kron(sparse(A), B)
 
+# sparse outer product
+kron(A::SparseVectorUnion, B::AdjOrTransSparseVectorUnion) = A .* B
+
 ## det, inv, cond
 
 inv(A::SparseMatrixCSC) = error("The inverse of a sparse matrix can often be dense and can cause the computer to run out of memory. If you are sure you have enough memory, please convert your matrix to a dense matrix.")