Better enum-based caching for preview images

packages/website/package.json

@@ -20,7 +20,9 @@
     "@sveltejs/adapter-node": "^5.1.1",
     "@sveltejs/kit": "^2.5.16",
     "@sveltejs/vite-plugin-svelte": "^3.1.1",
+    "@types/fnv-plus": "^1.3.2",
     "@types/node": "^20.14.2",
+    "@types/polka": "^0.5.7",
     "@types/sharedworker": "^0.0.115",
     "github-slugger": "^2.0.0",
     "glob": "^10.4.1",
@@ -76,6 +78,7 @@
     "Notes": "file:Notes-1.0.0.tgz",
     "acorn": "^8.12.0",
     "codemirror": "^6.0.1",
+    "fnv-plus": "^1.3.1",
     "magic-string": "^0.30.10",
     "octokit": "^3.2.1",
     "satori": "^0.10.14",