chore(deps): update dependency pug to v3

Author: renovate-bot

package.json

@@ -36,7 +36,7 @@
     "ghpages": "0.0.10",
     "node-sass": "4.11.0",
     "npm-run-all": "4.1.5",
-    "pug": "2.0.3",
+    "pug": "3.0.0",
     "pug-cli": "1.0.0-alpha6",
     "rimraf": "2.6.3",
     "sass-loader": "7.1.0",