Bump babel-plugin-istanbul from 5.2.0 to 6.0.0

Bumps [babel-plugin-istanbul](https://github.com/istanbuljs/babel-plugin-istanbul) from 5.2.0 to 6.0.0.
- [Release notes](https://github.com/istanbuljs/babel-plugin-istanbul/releases)
- [Changelog](https://github.com/istanbuljs/babel-plugin-istanbul/blob/master/CHANGELOG.md)
- [Commits](istanbuljs/babel-plugin-istanbul@v5.2.0...v6.0.0)

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

Author: dependabot-preview[bot]

package.json

@@ -62,7 +62,7 @@
     "@babel/preset-env": "^7.7.4",
     "babel-eslint": "^10.0.3",
     "babel-loader": "^8.0.6",
-    "babel-plugin-istanbul": "^5.2.0",
+    "babel-plugin-istanbul": "^6.0.0",
     "babelify": "^10.0.0",
     "browserify": "^16.5.0",
     "browserify-css": "^0.15.0",