bump ts-fsrs to 4.0.0@beta (#43)

Author: ishiko732

.nvmrc

@@ -0,0 +1 @@
+v18.20.3

package.json

@@ -28,7 +28,7 @@
     "papaparse": "^5.4.1",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",
-    "ts-fsrs": "^3.5.7"
+    "ts-fsrs": "4.0.0-beta"
   },
   "devDependencies": {
     "@types/bcrypt": "^5.0.2",