Update dependency rollup to v1.31.1 (#28)

Author: renovate-bot

package.json

@@ -47,7 +47,7 @@
     "npm-run-all": "4.1.5",
     "prettier": "1.19.1",
     "rimraf": "3.0.2",
-    "rollup": "1.31.0",
+    "rollup": "1.31.1",
     "shx": "0.3.2",
     "tslib": "1.10.0",
     "typescript": "3.7.5"