Bump webpack from 3.12.0 to 4.39.3

Bumps [webpack](https://github.com/webpack/webpack) from 3.12.0 to 4.39.3.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](webpack/webpack@v3.12.0...v4.39.3)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

package.json

@@ -53,7 +53,7 @@
     "shelljs": "0.8.3",
     "sshpk": "^1.16.1",
     "tunnel-agent": "^0.6.0",
-    "webpack": "^3.12.0",
+    "webpack": "^4.39.3",
     "webpack-bundle-analyzer": "^3.4.1"
   }
 }