Update miniflare to v3 (finally!)

Thanks to cloudflare/miniflare#639

Author: ajgeiss0702

package.json

@@ -33,7 +33,7 @@
 		"eslint": "^8.28.0",
 		"eslint-config-prettier": "^8.5.0",
 		"eslint-plugin-svelte3": "^4.0.0",
-		"miniflare": "^2.13.0",
+		"miniflare": "^3.20230922.0",
 		"postcss": "^8.4.23",
 		"prettier": "^2.8.0",
 		"prettier-plugin-svelte": "^2.8.1",