Fix reolink docs and add example of manual ffmpeg restream (#5165)

* Update camera_specific.md

* Update restream.md

docs/docs/configuration/camera_specific.md

@@ -107,6 +107,7 @@ According to [this discussion](https://github.com/blakeblackshear/frigate/issues
 
 ```yaml
 go2rtc:
+  streams:
     reolink: ffmpeg:http://reolink_ip/flv?port=1935&app=bcs&stream=channel0_main.bcs&user=username&password=password#video=copy#audio=copy#audio=opus
     reolink_sub: ffmpeg:http://reolink_ip/flv?port=1935&app=bcs&stream=channel0_ext.bcs&user=username&password=password
 

docs/docs/configuration/restream.md

@@ -57,7 +57,7 @@ cameras:
             - detect
 ```
 
-#### With Sub Stream
+### With Sub Stream
 
 Two connections are made to the camera. One for the sub stream, one for the restream, `record` connects to the restream.
 
@@ -103,3 +103,15 @@ cameras:
           roles:
             - detect
 ```
+
+## Advanced Restream Configurations
+
+The [exec](https://github.com/AlexxIT/go2rtc#source-exec) source in go2rtc can be used for custom ffmpeg commands. An example is below:
+
+NOTE: The output will need to be passed with two curly braces `{{output}}`
+
+```yaml
+go2rtc:
+  streams:
+    stream1: exec:ffmpeg -hide_banner -re -stream_loop -1 -i /media/BigBuckBunny.mp4 -c copy -rtsp_transport tcp -f rtsp {{output}}
+```