Bump postcss from 8.2.7 to 8.2.8

Bumps [postcss](https://github.com/postcss/postcss) from 8.2.7 to 8.2.8.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.2.7...8.2.8)

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

package.json

@@ -69,7 +69,7 @@
     "html-minifier": "^4.0.0",
     "material-design-color": "^2.3.2",
     "material-shadows": "^3.0.1",
-    "postcss": "^8.2.7",
+    "postcss": "^8.2.8",
     "postcss-inline-svg": "^5.0.0",
     "preact": "^10.5.12",
     "rimraf": "^3.0.2",