Add default image to CDN, favicon to registration, create logo

cdn/src/robocraft/favicon.rs

@@ -0,0 +1,7 @@
+use actix_web::{get, Responder, web::Data};
+
+#[get("/robocraft/favicon")]
+pub async fn get(cli: Data<crate::cli::CliArgs>) -> impl Responder {
+    let path = std::path::PathBuf::from(&cli.assets_robocraft).join("favicon.jpg");
+    actix_files::NamedFile::open_async(path).await
+}