Added web-components keyword to package.json

This adds the repository to https://customelements.io/ to make it easier
to find it.

Author: frederikschubert

package.json

@@ -13,7 +13,8 @@
   "keywords": [
     "angular",
     "angular2",
-    "grid"
+    "grid",
+    "web-components"
   ],
   "author": "Ben Morton <[email protected]> (http://bmorton.co.uk/)",
   "contributors": [