Serve gui from server

The server will serve all files in the ./www directory relative to
itself. The ./www/pkg is populated when running

    wasm-pack build --release --target web

from the /gui directory

srv/src/main.rs

@@ -1,15 +1,27 @@
 #[macro_use]
 extern crate rocket;
 
-use std::env;
+use std::{env, path::Path};
 
 use inkopslista_lib::{Item, ItemData};
-use rocket::{serde::json::Json, State};
+use rocket::{
+    fs::{FileServer, NamedFile},
+    serde::json::Json,
+    State,
+};
 use sqlite::ConnectionThreadSafe;
 
+/// The directory where the web files for the gui is stored.
+fn www_path() -> &'static Path {
+    Path::new("./www")
+}
+
+/// Serve `index.html` from [`www_path`].
 #[get("/")]
-fn index() -> &'static str {
-    "hello world"
+async fn index() -> NamedFile {
+    NamedFile::open(www_path().join("index.html"))
+        .await
+        .expect("index.html")
 }
 
 #[get("/api/list")]
@@ -67,4 +79,5 @@ fn rocket() -> _ {
     rocket::build()
         .manage(db)
         .mount("/", routes![index, get_list, put_list, delete_item])
+        .mount("/", FileServer::from(www_path()))
 }