Add voice guide

docs/guides/samples/audio_ffmpeg.cs

@@ -0,0 +1,9 @@
+private async Task SendAsync(IAudioClient client, string path)
+{
+    // Create FFmpeg using the previous example
+    var ffmpeg = CreateStream(path);
+    var output = ffmpeg.StandardOutput.BaseStream;
+    var discord = client.CreatePCMStream(1920);
+    await output.CopyToAsync(discord);
+    await discord.FlushAsync();
+}