chore(deps-dev): bump postcss from 8.2.15 to 8.3.5

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.15 to 8.3.5.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.2.15...8.3.5)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

package-lock.json

@@ -148,14 +148,14 @@
     "license-checker": "^25.0.0",
     "lint-staged": "=11.0.0",
     "local-web-server": "^4.2.1",
-    "mini-css-extract-plugin": "^1.6.0",
+    "mini-css-extract-plugin": "^1.6.2",
     "mocha": "=8.4.0",
     "nightwatch": "^1.7.7",
     "npm-audit-ci-wrapper": "^3.0.2",
     "npm-run-all": "^4.1.5",
     "oauth2-server": "^2.4.1",
     "open": "^8.2.0",
-    "postcss": "=8.2.15",
+    "postcss": "=8.3.5",
     "postcss-loader": "=4.3.0",
     "postcss-preset-env": "=6.7.0",
     "prettier": "^2.3.0",