Bump webpack-dev-server from 3.1.5 to 3.1.11 in /tool

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 3.1.5 to 3.1.11.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/master/CHANGELOG.md)
- [Commits](webpack/webpack-dev-server@v3.1.5...v3.1.11)

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

Author: dependabot[bot]

tool/package.json

@@ -57,7 +57,7 @@
     "url-loader": "^1.1.1",
     "webpack": "^4.16.5",
     "webpack-cli": "^3.1.0",
-    "webpack-dev-server": "^3.1.5",
+    "webpack-dev-server": "^3.1.11",
     "write-file-webpack-plugin": "^4.3.2"
   }
 }