Bump rollup from 1.32.1 to 2.6.1

Bumps [rollup](https://github.com/rollup/rollup) from 1.32.1 to 2.6.1.
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rollup/rollup/compare/v1.32.1...v2.6.1)

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

package.json

@@ -20,7 +20,7 @@
     "headr": "^0.0.4",
     "node-sass": "^4.13.0",
     "npm-run-all": "^4.1.5",
-    "rollup": "^1.16.2",
+    "rollup": "^2.6.1",
     "rollup-plugin-babel": "^4.3.3",
     "rollup-plugin-commonjs": "^10.0.0",
     "rollup-plugin-inject": "^3.0.0",