Add Prometheus metrics

src/middleware/metricsMiddleware.ts

@@ -0,0 +1,10 @@
+import { MiddlewareHandler } from '@hono/hono';
+
+import { httpRequestCounter } from '@/metrics.ts';
+
+export const metricsMiddleware: MiddlewareHandler = async (c, next) => {
+  const { method, path } = c.req;
+  httpRequestCounter.inc({ method, path });
+
+  await next();
+};