refactor(core): use fractional indexing for sorting (#5809)

use https://github.com/rocicorp/fractional-indexing to enable better sorting logic for crdt app

packages/frontend/core/package.json

@@ -61,6 +61,7 @@
     "cssnano": "^6.0.1",
     "dayjs": "^1.11.10",
     "foxact": "^0.2.20",
+    "fractional-indexing": "^3.2.0",
     "graphql": "^16.8.1",
     "idb": "^8.0.0",
     "image-blob-reduce": "^4.1.0",