chore(deps): bump postcss from 7.0.5 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 7.0.5 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@7.0.5...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package.json

@@ -69,7 +69,7 @@
     "node-sass": "9.0.0",
     "pixrem": "4.0.1",
     "pleeease-filters": "4.0.0",
-    "postcss": "7.0.5",
+    "postcss": "8.4.31",
     "postcss-inline-svg": "3.1.1",
     "postcss-loader": "3.0.0",
     "prettier": "1.18.2",