add package description

package.json

+{
+  "name": "chnet-xrf",
+  "version": "0.1.0",
+  "dependencies": {
+    "@types/jquery": "^3.2.16"
+  },
+  "description": "Web application to analyse XRF images",
+  "license": "EUPL",
+  "repository": {
+    "url": "https://baltig.infn.it/chnet/XRF-App"
+  }
+}