docs: add Swagger UI

Summary:

Test Plan:

package.json

@@ -4,6 +4,7 @@
     "deploy": "wrangler deploy --minify src/index.ts"
   },
   "dependencies": {
+    "@hono/swagger-ui": "^0.2.2",
     "@hono/zod-openapi": "^0.12.0",
     "gql.tada": "^1.7.4",
     "graphql-request": "^7.0.1",

src/index.ts

@@ -1,3 +1,4 @@
+import { swaggerUI } from "@hono/swagger-ui";
 import { OpenAPIHono } from "@hono/zod-openapi";
 
 const app = new OpenAPIHono();
@@ -14,7 +15,7 @@ app.route(
 );
 
 // The OpenAPI documentation will be available at /doc
-app.doc("/doc", {
+app.doc("/openapi.json", {
   openapi: "3.0.0",
   info: {
     version: "1.0.0",
@@ -22,4 +23,6 @@ app.doc("/doc", {
   },
 });
 
+app.get("/docs", swaggerUI({ url: "/openapi.json" }));
+
 export default app;