For FIFOs & pipes, this lets you decide whether Bun's process should remain alive until the pipe is closed.
By default, it is automatically managed. While the stream is open, the process remains alive and once the other end hangs up or the stream closes, the process exits.
If you previously called unref, you can call this again to re-enable automatic management.
Internally, it will reference count the number of times this is called. By default, that number is 1
If the file is not a FIFO or pipe, ref and unref do nothing. If the pipe is already closed, this does nothing.