feat: add 404 handling

src/app.ts

@@ -25,5 +25,18 @@ app.use(router);
 if (process.env.DEBUG === "true") {
 	app.use('/swagger', swaggerUi.serve, swaggerUi.setup(swaggerSpec));
 }
+
+// Handle 404s
+// https://stackoverflow.com/a/9802006
+app.use(function(req, res) {
+	res.status(404);
+
+	if (req.accepts('json')) {
+		res.json({ status: 'error', error: 'Not found' });
+		return;
+	}
+
+	res.type('txt').send('Not found');
+});
 app.listen(6567, () => console.log('(HTTP Server) Listening on port 6567.'));