docs: talk about the filter caps
docs: talk about the filter caps

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