docs: check for broken links in docs
docs: check for broken links in docs

The check is done using curl (if available). It lists the curl exit code + http
status code (for those > 399) together with the use of the url in the code. The
check is not fatal.

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