gnu: obs: Add support for webcams.

* gnu/packages/video.scm (obs)[inputs]: Add v4l-utils.

gnu/packages/video.scm

@@ -1326,6 +1326,7 @@ (define-public obs
        ("mesa" ,mesa)
        ("pulseaudio" ,pulseaudio)
        ("qt" ,qt)
+       ("v4l-utils" ,v4l-utils)
        ("zlib" ,zlib)))
     (synopsis "Live streaming software")
     (description "Open Broadcaster Software provides a graphical interface for