build: Add npm run pack to build binary package

Result expected in build/stage/

Relate-to: https://github.com/mapbox/node-sqlite3/pull/1028
Change-Id: If0fd4574924149a59d510914cb872eab259bc6d5
Signed-off-by: Philippe Coval <p.coval@samsung.com>

package.json

@@ -50,7 +50,8 @@
   "scripts": {
     "install": "node-pre-gyp install --fallback-to-build",
     "pretest": "node test/support/createdb.js",
-    "test": "mocha -R spec --timeout 480000"
+    "test": "mocha -R spec --timeout 480000",
+    "pack": "node-pre-gyp package"
   },
   "license": "BSD-3-Clause",
   "keywords": [