chore(deps): update dependency rollup to v1.21.0

Author: renovate-bot

package-lock.json

@@ -126,7 +126,7 @@
     "prompt": "1.0.0",
     "replace-in-file": "4.1.3",
     "rimraf": "2.6.3",
-    "rollup": "1.19.4",
+    "rollup": "1.21.0",
     "rollup-plugin-commonjs": "10.0.2",
     "rollup-plugin-json": "4.0.0",
     "rollup-plugin-node-resolve": "5.2.0",