limit the number of requests per second to 20 by default

this is still configurable
may make downloading some large images slightly slower
but reduces risks of the download failing altogether

src/arguments.rs

@@ -95,7 +95,7 @@ pub struct Arguments {
     /// This throttles the flow of image tile requests coming from your computer,
     /// reducing the risk of crashing the remote server of getting banned for making too many
     /// requests in a short succession.
-    #[arg(short = 'i', long, default_value = "0s", value_parser = parse_duration)]
+    #[arg(short = 'i', long, default_value = "50ms", value_parser = parse_duration)]
     pub min_interval: Duration,
 
     /// Maximum time between the beginning of a request and the end of a response before