add link to google cloud storage adapter in readme
add link to google cloud storage adapter in readme

We needed to have both AWS V3 and Google Storage adapters in place simultaneously, so the V2 driver was not an option as a work-around. - see https://github.com/thephpleague/flysystem/issues/448
hannesvdvreken/flysystem,mhlavac/flysystem,twistor/flysystem,twistor/flysystem,mhlavac/flysystem