Bump postcss from 8.4.20 to 8.4.21

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.20 to 8.4.21.
- [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/8.4.20...8.4.21)

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

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

package-lock.json

@@ -2835,9 +2835,9 @@
       "dev": true
     },
     "postcss": {
-      "version": "8.4.20",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.20.tgz",
-      "integrity": "sha512-6Q04AXR1212bXr5fh03u8aAwbLxAQNGQ/Q1LNa0VfOI06ZAlhPHtQvE4OIdpj4kLThXilalPnmDSOD65DcHt+g==",
+      "version": "8.4.21",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.21.tgz",
+      "integrity": "sha512-tP7u/Sn/dVxK2NnruI4H9BG+x+Wxz6oeZ1cJ8P6G/PZY0IKk4k/63TDsQf2kQq3+qoJeLm2kIBUNlZe3zgb4Zg==",
       "dev": true,
       "requires": {
         "nanoid": "^3.3.4",

package.json

@@ -26,7 +26,7 @@
   "devDependencies": {
     "autoprefixer": "^10.4.13",
     "eslint-plugin-compat": "^4.0.2",
-    "postcss": "^8.4.20",
+    "postcss": "^8.4.21",
     "postcss-cli": "^10.1.0",
     "prettier": "2.8.1",
     "xo": "^0.53.1"