Update builders for libavdevice, pkg-config; add note about ffmpeg device support

.github/workflows/macos_test.yml

@@ -26,7 +26,8 @@ jobs:
             ffmpeg \
             libdeflate \
             libunistring \
-            ncurses
+            ncurses \
+            pkg-config
 
       - uses: actions/checkout@v2
 

.github/workflows/ubuntu_test.yml

@@ -28,6 +28,7 @@ jobs:
             ffmpeg \
             libavcodec-dev \
             libavformat-dev \
+            libavdevice-dev \
             libavutil-dev \
             libdeflate-dev \
             libncurses-dev \

README.md

@@ -112,7 +112,7 @@ may well be possible to use still older versions. Let me know of any successes!
 * (build+runtime) GNU [libunistring](https://www.gnu.org/software/libunistring/) 0.9.10+
 * (OPTIONAL) (build+runtime) [libgpm](https://www.nico.schottelius.org/software/gpm/) 1.20+
 * (OPTIONAL) (build+runtime) From QR-Code-generator: [libqrcodegen](https://github.com/nayuki/QR-Code-generator) 1.5.0+
-* (OPTIONAL) (build+runtime) From [FFmpeg](https://www.ffmpeg.org/): libswscale 5.0+, libavformat 57.0+, libavutil 56.0+
+* (OPTIONAL) (build+runtime) From [FFmpeg](https://www.ffmpeg.org/): libswscale 5.0+, libavformat 57.0+, libavutil 56.0+, libavdevice 57.0+
 * (OPTIONAL) (build+runtime) [OpenImageIO](https://github.com/OpenImageIO/oiio) 2.15.0+, requires C++
 * (OPTIONAL) (testing) [Doctest](https://github.com/onqtam/doctest) 2.3.5+
 * (OPTIONAL) (documentation) [pandoc](https://pandoc.org/index.html) 1.19.2+

doc/man/man3/notcurses_visual.3.md

@@ -132,6 +132,8 @@ If Notcurses was built against a multimedia engine (FFMpeg or OpenImageIO),
 image and video files can be loaded into visuals using
 **ncvisual_from_file**. **ncvisual_from_file** discovers the container
 and codecs, but does not verify that the entire file is well-formed.
+If Notcurses was built against FFMpeg, **ncvisual_from_file** can also handle
+multimedia devices such as webcams.
 **ncvisual_decode** ought be invoked to recover subsequent frames, once
 per frame. **ncvisual_decode_loop** will return to the first frame,
 as if **ncvisual_decode** had never been called.