chore(deps-dev): update rollup requirement from 1.19.3 to 1.19.4 (#309)

Updates the requirements on [rollup](https://github.com/rollup/rollup) to permit the latest version.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](rollup/rollup@v1.19.3...v1.19.4)

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

package.json

@@ -61,7 +61,7 @@
     "npm-run-all": "4.1.5",
     "prettier": "1.18.2",
     "rimraf": "2.6.3",
-    "rollup": "1.19.3",
+    "rollup": "1.19.4",
     "rollup-plugin-prettier": "0.6.0"
   },
   "keywords": [