upgrade: postcss (#18)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-POSTCSS-5926692

Co-authored-by: snyk-bot <snyk-bot@snyk.io>

package.json

@@ -41,7 +41,7 @@
     "iconoir": "^6.10.0",
     "modern-diacritics": "^2.3.0",
     "next": "13.4.12",
-    "postcss": "^8.4.27",
+    "postcss": "^8.4.31",
     "postcss-preset-env": "^9.1.0",
     "react": "18.2.0",
     "react-dom": "18.2.0",

yarn.lock

@@ -3579,10 +3579,10 @@ postcss@8.4.14:
     picocolors "^1.0.0"
     source-map-js "^1.0.2"
 
-postcss@^8.4.27:
-  version "8.4.27"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.27.tgz#234d7e4b72e34ba5a92c29636734349e0d9c3057"
-  integrity sha512-gY/ACJtJPSmUFPDCHtX78+01fHa64FaU4zaaWfuh1MhGJISufJAH4cun6k/8fwsHYeK4UQmENQK+tRLCFJE8JQ==
+postcss@^8.4.31:
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
     nanoid "^3.3.6"
     picocolors "^1.0.0"