feat(excel): group entries by date, join names with ' & '

package.json

@@ -5,6 +5,6 @@
   "type": "module",
   "scripts": {
     "start": "npx serve . -p 3001",
-    "test": "node tests/algorithm.test.mjs && node tests/data.test.mjs"
+    "test": "node tests/algorithm.test.mjs && node tests/data.test.mjs && node tests/excel.test.mjs"
   }
 }