Function spawn_previewer 

pub fn spawn_previewer(
    rx_request: impl Receiver<PreviewRequest> + 'static,
    tx_preview: impl Sender<(PreviewSource, PreviewContent)> + 'static,
    tx_log: impl Sender<(String, Vec<LogEntry>)> + 'static,
    picker: Picker,
    preview_command: Option<String>,
    delimiter: String,
    log_max_entries: usize,
)

Spawn the preview worker thread.

This function spawns a background thread that receives file paths and generates preview content, sending results back through the provided channel.