Add icon sizes to config

Icon sizes are stored as a zoom percentage. This may need to be updated
by a programmer with better ideas, but it seems a bit nicer than storing
the size in pixels and presenting that to the user.

src/dialog.rs

@@ -209,9 +209,10 @@ struct App {
 impl App {
     fn rescan_tab(&self) -> Command<Message> {
         let location = self.tab.location.clone();
+        let icon_sizes = self.tab.config.icon_sizes;
         Command::perform(
             async move {
-                match tokio::task::spawn_blocking(move || location.scan()).await {
+                match tokio::task::spawn_blocking(move || location.scan(icon_sizes)).await {
                     Ok(items) => message::app(Message::TabRescan(items)),
                     Err(err) => {
                         log::warn!("failed to rescan: {}", err);