feat: display error overlay (#607)

Co-authored-by: Marco Pasqualetti <marco.pasqualetti@live.com>

crates/tuono_internal/src/config.rs

@@ -10,7 +10,17 @@ pub struct ServerConfig {
     pub port: u16,
 }
 
-#[derive(Deserialize, Serialize, Debug, Clone)]
+impl Default for ServerConfig {
+    fn default() -> Self {
+        ServerConfig {
+            host: "localhost".to_string(),
+            origin: None,
+            port: 3000,
+        }
+    }
+}
+
+#[derive(Deserialize, Serialize, Debug, Clone, Default)]
 pub struct Config {
     pub server: ServerConfig,
 }
@@ -23,3 +33,17 @@ impl Config {
             .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_config_default() {
+        let config = Config::default();
+
+        assert_eq!(config.server.host, "localhost".to_string());
+        assert_eq!(config.server.origin, None);
+        assert_eq!(config.server.port, 3000);
+    }
+}