chore(deps-dev): bump rollup from 2.20.0 to 2.21.0

Bumps [rollup](https://github.com/rollup/rollup) from 2.20.0 to 2.21.0.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](rollup/rollup@v2.20.0...v2.21.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -65,7 +65,7 @@
  "jasmine-core": "3.5.0",
  "prettier": "2.0.5",
  "rimraf": "3.0.2",
- "rollup": "2.20.0",
+ "rollup": "2.21.0",
  "rollup-plugin-prettier": "2.1.0",
  "rollup-plugin-strip-banner": "2.0.0",
  "tmp": "0.2.1"