refacto: Changing some docker images to hardened non-root ones + README update

server/healthcheck.js

@@ -0,0 +1,8 @@
+import http from "http";
+
+const port = Number(process.env.PORT ?? 8080);
+http
+  .get(`http://localhost:${port}/api/config`, (res) => {
+    process.exit(res.statusCode === 200 ? 0 : 1);
+  })
+  .on("error", () => process.exit(1));