Merge pull request #1467 from textpattern/dependabot/npm_and_yarn/postcss-8.5.21

Bump postcss from 8.5.19 to 8.5.21

Author: petecooper

package.json

@@ -31,7 +31,7 @@
     "cross-env": "10.1.0",
     "css-loader": "7.1.4",
     "mini-css-extract-plugin": "2.10.2",
-    "postcss": "8.5.19",
+    "postcss": "8.5.21",
     "postcss-loader": "8.2.1",
     "postcss-scss": "4.0.9",
     "sass": "1.101.0",