build(deps): bump postcss from 7.0.27 to 7.0.28

Bumps [postcss](https://github.com/postcss/postcss) from 7.0.27 to 7.0.28.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/master/CHANGELOG.md)
- [Commits](postcss/postcss@7.0.27...7.0.28)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -59,7 +59,7 @@
     "ncp": "^2.0.0",
     "node-version-data": "^1.1.0",
     "npm-run-all": "^4.1.5",
-    "postcss": "^7.0.27",
+    "postcss": "^7.0.28",
     "sass": "^1.26.5",
     "semver": "^7.3.2",
     "strftime": "^0.10.0"