Bump cssnano from 4.1.11 to 5.1.14 in /web

Bumps [cssnano](https://github.com/cssnano/cssnano) from 4.1.11 to 5.1.14.
- [Release notes](https://github.com/cssnano/cssnano/releases)
- [Commits](https://github.com/cssnano/cssnano/compare/v4.1.11...cssnano@5.1.14)

---
updated-dependencies:
- dependency-name: cssnano
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

web/package.json

@@ -17,7 +17,7 @@
     "babel-loader": "^8.2.2",
     "clean-webpack-plugin": "^3.0.0",
     "css-loader": "^5.0.1",
-    "cssnano": "^4.1.10",
+    "cssnano": "^5.1.14",
     "extra-watch-webpack-plugin": "^1.0.3",
     "fs-extra": "^9.0.1",
     "html-webpack-harddisk-plugin": "^1.0.2",