⬆️ Update rollup requirement to ^0.60.0

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](https://github.com/rollup/rollup/commits/v0.60.0)

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

package.json

@@ -33,7 +33,7 @@
   "devDependencies": {
     "chai": "^4.1.2",
     "holding": "^3.0.2",
-    "rollup": "^0.59.3",
+    "rollup": "^0.60.0",
     "fs-extra": "^6.0.1",
     "superagent": "^3.8.2"
   },