add: 404 not found

frontend/static/js/views/PageNotFoundView.js

@@ -0,0 +1,14 @@
+import AbstractView from "./AbstractView.js";
+
+export default class extends AbstractView {
+    constructor(params) {
+        super(params, "Dashboard");
+    }
+
+	async getHtml() {
+		return `
+			<h1>404 Bozo</h1>
+			<p>Git gud</p>
+		`;
+	}
+}