feat: add /calendar/foo API route

src/calendar.rs

···
+use axum::extract::Path;
+
+pub(crate) async fn route(Path(_path): Path<String>) -> String {
+    "hello world!".to_string()
+}

src/main.rs

···
+mod calendar;
+
 #[cfg(feature = "ssr")]
 #[tokio::main]
 async fn main() {
-    use axum::Router;
+    use axum::{routing::get, Router};
     use leptos::logging::log;
     use leptos::prelude::*;
     use leptos_axum::{generate_route_list, LeptosRoutes};
···
     let routes = generate_route_list(App);
 
     let app = Router::new()
+        .route("/calendar/{id}", get(calendar::route))
         .leptos_routes(&leptos_options, routes, {
             let leptos_options = leptos_options.clone();
             move || shell(leptos_options.clone())