Add method to call custom commands

src/lib.rs

@@ -502,6 +502,13 @@ impl Mpv {
         }
     }
 
+    /// Run a custom command.
+    /// This should only be used if the desired command is not implemented
+    /// with [MpvCommand].
+    pub fn run_command_raw(&self, command: &str, args: &[&str]) -> Result<(), Error> {
+        run_mpv_command(self, command, args)
+    }
+
     pub fn playlist_add(
         &self,
         file: &str,