Update Storybook to 6

package.json

@@ -21,11 +21,11 @@
     "@babel/preset-react": "^7.10.0",
     "@babel/preset-typescript": "^7.9.0",
     "@rails/webpacker": "^5.1.1",
-    "@storybook/addon-actions": "^5.3.19",
-    "@storybook/addon-knobs": "^5.3.19",
-    "@storybook/addon-links": "^5.3.19",
-    "@storybook/addons": "^5.3.19",
-    "@storybook/react": "^5.3.19",
+    "@storybook/addon-actions": "^6.0.2",
+    "@storybook/addon-knobs": "^6.0.2",
+    "@storybook/addon-links": "^6.0.2",
+    "@storybook/addons": "^6.0.2",
+    "@storybook/react": "^6.0.2",
     "@testing-library/jest-dom": "^5.11.1",
     "@testing-library/react": "^10.4.7",
     "@testing-library/react-hooks": "^3.3.0",