Add README to apt-cacher-ng
Add README to apt-cacher-ng

jakirkham/dockerfiles,adammcarth/dockerfiles,atyenoria/dockerfiles,adammcarth/dockerfiles,jakirkham/dockerfiles,adammcarth/dockerfiles,jakirkham/dockerfiles,rot26/dockerfiles,atyenoria/dockerfiles,jakirkham/dockerfiles,jakirkham/dockerfiles,atyenoria/dockerfiles,pmav99/dockerfiles,atyenoria/dockerfiles,rot26/dockerfiles,pmav99/dockerfiles,pmav99/dockerfiles,adammcarth/dockerfiles,pmav99/dockerfiles,rot26/dockerfiles,rot26/dockerfiles