Downstream test against ApproxFunBase (#339)

* Downstream test against ApproxFun

* Test only against ApproxFunBase

Author: jishnub

.github/workflows/downstream.yml

@@ -31,6 +31,7 @@ jobs:
         os: [ubuntu-latest]
         package:
           - {repo: BlockBandedMatrices.jl, group: JuliaLinearAlgebra}
+          - {repo: ApproxFunBase.jl, group: JuliaApproximation}
           # - {repo: InfiniteLinearAlgebra.jl, group: JuliaLinearAlgebra}
 
     steps: