chore(package): update @storybook/addon-viewport to version 5.3.18

Closes #23

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "@storybook/addon-knobs": "^5.3.18",
     "@storybook/addon-storyshots": "^5.3.18",
     "@storybook/addon-storyshots-puppeteer": "^5.3.18",
-    "@storybook/addon-viewport": "^4.0.2",
+    "@storybook/addon-viewport": "^5.3.18",
     "@storybook/react": "^4.0.2",
     "babel-core": "^7.0.0-bridge.0",
     "babel-jest": "^23.6.0",