Ajout commande npm pour valider xml extrait

package.json

@@ -22,6 +22,7 @@
     "preprocess": "node coauth.js prepare ./data/dblp.xml",
     "coauth": "node coauth.js --name \"Fabien Delorme\" -v",
     "extract": "node extract.js --name \"Fabien Delorme\" -v",
+    "validate": "xmllint --noout --dtdvalid ./data/extract.dtd ./data/extract.xml",
     "xslt": "xsltproc -o extract.html convert.xsl ./data/extract.xml"
   },
   "engines": {