Docker: Add doc of adding new installers.
Docker: Add doc of adding new installers.

ycool/apollo,jinghaomiao/apollo,wanglei828/apollo,xiaoxq/apollo,ApolloAuto/apollo,ycool/apollo,wanglei828/apollo,jinghaomiao/apollo,xiaoxq/apollo,ApolloAuto/apollo,wanglei828/apollo,jinghaomiao/apollo,jinghaomiao/apollo,xiaoxq/apollo,ApolloAuto/apollo,wanglei828/apollo,jinghaomiao/apollo,ApolloAuto/apollo,xiaoxq/apollo,xiaoxq/apollo,ycool/apollo,jinghaomiao/apollo,ApolloAuto/apollo,ycool/apollo,ycool/apollo,wanglei828/apollo,wanglei828/apollo,ycool/apollo,ApolloAuto/apollo,xiaoxq/apollo