chore: add dependency to conventional-changelog-cli

The package is used by the npm preversion script for generating
changelog.

Author: sis0k0

package.json

@@ -79,6 +79,7 @@
     "@ngtools/webpack": "~1.9.0",
     "@types/node": "^8.0.0",
     "source-map-support": "^0.5.0",
-    "typescript": "^2.6.1"
+    "typescript": "^2.6.1",
+    "conventional-changelog-cli": "1.3.21"
   }
 }