logging for mpv commands

src/mpv/handle.rs

@@ -103,6 +103,7 @@ impl Handle {
             .map(CString::new)
             .map(Result::unwrap)
             .collect();
+        event!(Level::DEBUG, "sending command to mpv: {:?}", args);
         let mut args: Vec<*const c_char> = args
             .iter()
             .map(CString::as_c_str)