Merge pull request #1140 from textpattern/dependabot/npm_and_yarn/postcss-8.5.6

Bump postcss from 8.5.3 to 8.5.6

Author: petecooper

package.json

@@ -22,7 +22,7 @@
     "cross-env": "7.0.3",
     "css-loader": "7.1.2",
     "mini-css-extract-plugin": "2.9.2",
-    "postcss": "8.5.3",
+    "postcss": "8.5.6",
     "postcss-loader": "8.1.1",
     "postcss-scss": "4.0.9",
     "sass": "1.86.0",