Fix npm run lint by ignoring *.md files in data

Usually prettier can switch automatically to check Markdown and format it. However, this prettier config forces the JSON formatter for all files.

package.json

@@ -12,7 +12,7 @@
   "license": "ISC",
   "main": "build.js",
   "scripts": {
-    "lint": "prettier --check data",
+    "lint": "prettier --check 'data/**/!(*.md)'",
     "lint:fix": "prettier --write data",
     "build": "node scripts/build.js",
     "dist": "node scripts/dist.js",