added predix example file

examples/routePrefix.ts

@@ -0,0 +1,39 @@
+import {
+  Application,
+  Router,
+} from "../mod.ts";
+const router = new Router({
+  prefix: "/prefix",
+  // strict: true,
+});
+
+const port = 4000;
+
+const server = new Application();
+
+server.use(
+  router.routes(),
+  router.allowedMethods(),
+);
+
+router
+  .get("/", ({ response }: { response: any }) => {
+    response.status = 200;
+    response.body = { msg: "Prefix works" };
+  })
+  .get(
+    "/:id",
+    ({ params, response }: { params: { id: string }; response: any }) => {
+      response.body = `prefix w/ id: ${params.id}`;
+    },
+  )
+  .get(
+    "/test",
+    ({ params, response }: { params: { id: string }; response: any }) => {
+      response.body = `test`;
+    },
+  );
+
+console.log("server running");
+
+await server.listen({ port });