crav1e: Add bitrate option

Currently pinned to one pass only, since, as far as I know, this is
all rav1e currently supports.

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

src/capi.rs

@@ -206,6 +206,7 @@ unsafe fn option_match(
 
         "tune" => enc.tune = value.parse().map_err(|_| ())?,
         "quantizer" => enc.quantizer = value.parse().map_err(|_| ())?,
+        "bitrate" => enc.bitrate = value.parse().map_err(|_| ())?,
 
         "key_frame_interval" => enc.max_key_frame_interval = value.parse().map_err(|_| ())?,
         "min_key_frame_interval" => enc.min_key_frame_interval = value.parse().map_err(|_| ())?,