[Request] manually mark files as ignored

[kerhbal]

The whole point of this is not to auto start downloading the files I don't want after seedsync is restarted.

Right now, if I manually stop a file to be downloaded, then it will be fine until I restart the seedsync, which is often, since we need to restart it for every setting change.

As different from pattern based auto queue, this brings more flexibility.

Thanks for the consideration!