docs: update synchronization document a little
docs: update synchronization document a little

StreamUtils/gstreamer,justinjoy/gstreamer,collects/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,jpakkane/gstreamer,collects/gstreamer,lovebug356/gstreamer,cablelabs/gstreamer,shelsonjava/gstreamer,jpakkane/gstreamer,StreamUtils/gstreamer,mparis/gstreamer,jpakkane/gstreamer,krichter722/gstreamer,collects/gstreamer,ensonic/gstreamer,centricular/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,jpakkane/gstreamer,cfoch/gstreamer,krieger-od/gstreamer,jpakkane/gstreamer,mparis/gstreamer,ensonic/gstreamer,krieger-od/gstreamer,Lachann/gstreamer,Lachann/gstreamer,cablelabs/gstreamer,Lachann/gstreamer,lovebug356/gstreamer,shelsonjava/gstreamer,surround-io/gstreamer,krieger-od/gstreamer,surround-io/gstreamer,collects/gstreamer,surround-io/gstreamer,cfoch/gstreamer,lubosz/gstreamer,krieger-od/gstreamer,ensonic/gstreamer,lubosz/gstreamer,lovebug356/gstreamer,centricular/gstreamer,justinjoy/gstreamer,surround-io/gstreamer,Lachann/gstreamer,lubosz/gstreamer,StreamUtils/gstreamer,ensonic/gstreamer,lovebug356/gstreamer,justinjoy/gstreamer,krichter722/gstreamer,cfoch/gstreamer,lubosz/gstreamer,krichter722/gstreamer,cfoch/gstreamer,StreamUtils/gstreamer,ensonic/gstreamer,centricular/gstreamer,lovebug356/gstreamer,justinjoy/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,collects/gstreamer,Lachann/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,mparis/gstreamer,krieger-od/gstreamer,mparis/gstreamer,cablelabs/gstreamer,lubosz/gstreamer,surround-io/gstreamer,cablelabs/gstreamer,cablelabs/gstreamer,justinjoy/gstreamer,cfoch/gstreamer,centricular/gstreamer,shelsonjava/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,mparis/gstreamer