Add integration badge

Author: jishnub

README.md

@@ -4,6 +4,7 @@ Support for orthogonal polynomial-based spaces in ApproxFun
 [![](https://img.shields.io/badge/docs-stable-blue.svg)](https://JuliaApproximation.github.io/ApproxFun.jl/stable)
 [![](https://img.shields.io/badge/docs-latest-blue.svg)](https://JuliaApproximation.github.io/ApproxFun.jl/latest)
 [![CI](https://github.com/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl/actions/workflows/ci.yml/badge.svg)](https://github.com/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl/actions/workflows/ci.yml)
+[![IntegrationTest](https://github.com/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl/actions/workflows/downstream.yml/badge.svg)](https://github.com/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl/actions/workflows/downstream.yml)
 [![codecov](https://codecov.io/gh/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/JuliaApproximation/ApproxFunOrthogonalPolynomials.jl)
 [![deps](https://juliahub.com/docs/ApproxFunOrthogonalPolynomials/deps.svg)](https://juliahub.com/ui/Packages/ApproxFunOrthogonalPolynomials/bk9eW?t=2)
 [![version](https://juliahub.com/docs/ApproxFunOrthogonalPolynomials/version.svg)](https://juliahub.com/ui/Packages/ApproxFunOrthogonalPolynomials/bk9eW)