Update dependency rollup to v1.15.6

Author: renovate-bot

package.json

@@ -26,7 +26,7 @@
     "postcss-cli": "6.1.2",
     "postcss-preset-env": "6.6.0",
     "prettier": "1.17.0",
-    "rollup": "1.15.2",
+    "rollup": "1.15.6",
     "rollup-plugin-node-resolve": "4.2.4",
     "serve": "11.0.0"
   }

yarn.lock

@@ -4317,10 +4317,10 @@ [email protected]:
     is-module "^1.0.0"
     resolve "^1.10.0"
 
-[email protected].2:
-  version "1.15.2"
-  resolved "https://registry.yarnpkg.com/rollup/-/rollup-1.15.2.tgz#676feb0e73c8f99f75e0078b331a576c56354df6"
-  integrity sha512-NsH0Mjqk/RtlhSIJopNUiCYi3r3zudHxg9Cj6Or96QnJw/suab0/PjL50/GRNE5omvXEG2F9K4a334ddvA1Txg==
+[email protected].6:
+  version "1.15.6"
+  resolved "https://registry.yarnpkg.com/rollup/-/rollup-1.15.6.tgz#caf0ed28d2d78e3a59c1398e5a3695fb600a0ef0"
+  integrity sha512-s3Vn3QJQ5YVFfIG4nXoG9VdL1I37IZsft+4ZyeBhxE0df1kCFz9e+4bEAbR4mKH3pvBO9e9xjdxWPhhIp0r9ow==
   dependencies:
     "@types/estree" "0.0.39"
     "@types/node" "^12.0.8"