chore(deps-dev): bump postcss in /examples/druxt-site (#663)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.14 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@8.4.14...8.4.31)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

examples/druxt-site/yarn.lock

@@ -11327,7 +11327,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"nanoid@npm:^3.1.23, nanoid@npm:^3.3.1, nanoid@npm:^3.3.4":
+"nanoid@npm:^3.1.23, nanoid@npm:^3.3.1":
   version: 3.3.4
   resolution: "nanoid@npm:3.3.4"
   bin:
@@ -11336,6 +11336,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"nanoid@npm:^3.3.6":
+  version: 3.3.6
+  resolution: "nanoid@npm:3.3.6"
+  bin:
+    nanoid: bin/nanoid.cjs
+  checksum: 7d0eda657002738aa5206107bd0580aead6c95c460ef1bdd0b1a87a9c7ae6277ac2e9b945306aaa5b32c6dcb7feaf462d0f552e7f8b5718abfc6ead5c94a71b3
+  languageName: node
+  linkType: hard
+
 "nanomatch@npm:^1.2.9":
   version: 1.2.13
   resolution: "nanomatch@npm:1.2.13"
@@ -13339,13 +13348,13 @@ __metadata:
   linkType: hard
 
 "postcss@npm:^8.1.10, postcss@npm:^8.2.15, postcss@npm:^8.4.14, postcss@npm:latest":
-  version: 8.4.14
-  resolution: "postcss@npm:8.4.14"
+  version: 8.4.31
+  resolution: "postcss@npm:8.4.31"
   dependencies:
-    nanoid: ^3.3.4
+    nanoid: ^3.3.6
     picocolors: ^1.0.0
     source-map-js: ^1.0.2
-  checksum: fe58766ff32e4becf65a7d57678995cfd239df6deed2fe0557f038b47c94e4132e7e5f68b5aa820c13adfec32e523b693efaeb65798efb995ce49ccd83953816
+  checksum: 1d8611341b073143ad90486fcdfeab49edd243377b1f51834dc4f6d028e82ce5190e4f11bb2633276864503654fb7cab28e67abdc0fbf9d1f88cad4a0ff0beea
   languageName: node
   linkType: hard