chore: rework into commonjs package

Signed-off-by: Patrick Kollitsch <[email protected]>

Author: davidsneighbour

packages/frontmatter-config/index.js renamed to packages/frontmatter-config/index.cjs

@@ -11,10 +11,11 @@
     "fixpack": "fixpack",
     "update": "npm-check-updates -u && npm install && git add package* && fixpack && git commit -m \"chore(deps): update dependencies\""
   },
-  "main": "index.js",
+  "main": "index.cjs",
   "engines": {
     "node": ">=22.1.0",
     "npm": ">=10.8.0"
   },
-  "gitHead": "515736c9b5186fe57ad4e73dbbf6915b76641277"
+  "gitHead": "515736c9b5186fe57ad4e73dbbf6915b76641277",
+  "type": "commonjs"
 }