Add ContinuumArrays.jl to downstream tests (#481)

Author: dlfivefifty

.github/workflows/downstream.yml

@@ -36,6 +36,7 @@ jobs:
         package:
           - {repo: BlockBandedMatrices.jl, group: JuliaLinearAlgebra}
           - {repo: ApproxFunBase.jl, group: JuliaApproximation}
+          - {repo: ContinuumArrays.jl, group: JuliaApproximation}
           - {repo: LazyArrays.jl, group: JuliaArrays}
           - {repo: LazyBandedMatrices.jl, group: JuliaLinearAlgebra}
           - {repo: InfiniteLinearAlgebra.jl, group: JuliaLinearAlgebra}