Bump @rollup/plugin-commonjs from 20.0.0 to 21.0.0

Bumps [@rollup/plugin-commonjs](https://github.com/rollup/plugins/tree/HEAD/packages/commonjs) from 20.0.0 to 21.0.0.
- [Release notes](https://github.com/rollup/plugins/releases)
- [Changelog](https://github.com/rollup/plugins/blob/master/packages/commonjs/CHANGELOG.md)
- [Commits](https://github.com/rollup/plugins/commits/commonjs-v21.0.0/packages/commonjs)

---
updated-dependencies:
- dependency-name: "@rollup/plugin-commonjs"
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

package.json

@@ -56,7 +56,7 @@
     "@babel/preset-env": "^7.4.4",
     "@openlayers/eslint-plugin": "^4.0.0",
     "@rollup/plugin-babel": "^5.3.0",
-    "@rollup/plugin-commonjs": "^20.0.0",
+    "@rollup/plugin-commonjs": "^21.0.0",
     "@rollup/plugin-node-resolve": "^13.0.0",
     "@types/arcgis-rest-api": "^10.4.4",
     "@types/geojson": "^7946.0.7",