chore(deps): update dependency rollup to v2.21.0

Author: renovate-bot

package-lock.json

@@ -54,7 +54,7 @@
     "jest": "26.1.0",
     "lint-staged": "10.2.11",
     "prettier": "2.0.5",
-    "rollup": "2.18.1",
+    "rollup": "2.21.0",
     "rollup-plugin-terser": "6.1.0",
     "sinon": "9.0.2",
     "start-server-and-test": "1.11.0"