Add README.md to ignored files
Add README.md to ignored files

[#136438447]

Signed-off-by: Keaty <ba27100af1ae477f2abedd28f15b1dd208b1f48a@pivotal.io>

cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci,cloudfoundry/buildpacks-ci