Fix postcss dependency resolution warnings

After running `yarn install`, the output includes these warnings:

```
➤ YN0002: │ stylelint-config-recommended-scss@npm:5.0.2 [f9349] doesn't provide postcss (paa625), requested by postcss-scss
➤ YN0002: │ stylelint-config-standard-scss@npm:3.0.0 [21994] doesn't provide postcss (pd7477), requested by stylelint-config-recommended-scss
➤ YN0002: │ stylelint-config-gds@npm:0.2.0 [93ec2] doesn't provide postcss (p8e745), requested by stylelint-config-standard-scss
```

This fixes the above warnings as recommended in this
thread - [stylelint-scss/stylelint-config-recommended-scss#89](stylelint-scss/stylelint-config-recommended-scss#89) (comment)

.yarnrc.yml

@@ -1,2 +1,12 @@
 yarnPath: .yarn/releases/yarn-3.5.0.cjs
-nodeLinker: node-modules
+nodeLinker: node-modules
+packageExtensions:
+  stylelint-config-recommended-scss@*:
+    peerDependencies:
+      postcss: '8'
+  stylelint-config-standard-scss@*:
+    peerDependencies:
+      postcss: '8'
+  stylelint-config-gds@*:
+    peerDependencies:
+      postcss: '8'