Add configurable src generator interface: IResponsiveGenerateSrc
There are two built-in generator service: default one: ResponsiveGenerateSrcService and the round size RoundGenerateSrcService that has less image size variation which will reduce the image numbers in cache.
to use ResponsiveImage module, you need to add a provider for token: SRC_GENERATOR_SERVICE
For example, if you want to use the default service:
{provide: SRC_GENERATOR_SERVICE, useClass: ResponsiveGenerateSrcService}