Bump webpack from 4.39.2 to 4.39.3 in /slides (#198)

Bumps [webpack](https://github.com/webpack/webpack) from 4.39.2 to 4.39.3.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](webpack/webpack@v4.39.2...v4.39.3)

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

Author: dependabot-preview[bot]

slides/package-lock.json

@@ -16,7 +16,7 @@
     "mini-css-extract-plugin": "^0.8.0",
     "pug": "^2.0.4",
     "pug-loader": "^2.4.0",
-    "webpack": "^4.39.2",
+    "webpack": "^4.39.3",
     "webpack-cli": "^3.3.7"
   },
   "scripts": {