fix: package.json & yarn.lock to reduce vulnerabilities

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

package.json

@@ -82,7 +82,7 @@
  "passport": "^0.5.2",
  "passport-jwt": "^4.0.0",
  "passport-local": "^1.0.0",
- "postcss": "^8.4.12",
+ "postcss": "^8.4.31",
  "prettier": "^2.5.1",
  "prop-types": "^15.8.1",
  "react": "^17.0.2",

yarn.lock

@@ -5192,11 +5192,16 @@ nan@^2.13.2:
  resolved "https://registry.yarnpkg.com/nan/-/nan-2.15.0.tgz#3f34a473ff18e15c1b5626b62903b5ad6e665fee"
  integrity sha512-8ZtvEnA2c5aYCZYd1cvgdnU6cqwixRoYg70xPLWUws5ORTa/lnw+u4amixRS/Ac5U5mQVgp9pnlSUnbNWFaWZQ==
 
-nanoid@^3.1.30, nanoid@^3.3.1:
+nanoid@^3.1.30:
  version "3.3.1"
  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.1.tgz#6347a18cac88af88f58af0b3594b723d5e99bb35"
  integrity sha512-n6Vs/3KGyxPQd6uO0eH4Bv0ojGSUvuLlIHtC3Y0kEO23YRge8H9x1GCzLn28YX0H66pMkxuaeESFq4tKISKwdw==
 
+nanoid@^3.3.6:
+ version "3.3.6"
+ resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
+ integrity sha512-BGcqMMJuToF7i1rt+2PWSNVnWIkGCU78jBG3RxO/bZlnZPK2Cmi2QaffxGO/2RvWi9sL+FAiRiXMgsyxQ1DIDA==
+
 natural-compare@^1.4.0:
  version "1.4.0"
  resolved "https://registry.yarnpkg.com/natural-compare/-/natural-compare-1.4.0.tgz#4abebfeed7541f2c27acfb29bdbbd15c8d5ba4f7"
@@ -5737,12 +5742,12 @@ postcss@8.4.5:
  picocolors "^1.0.0"
  source-map-js "^1.0.1"
 
-postcss@^8.4.12:
- version "8.4.12"
- resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.12.tgz#1e7de78733b28970fa4743f7da6f3763648b1905"
- integrity sha512-lg6eITwYe9v6Hr5CncVbK70SoioNQIq81nsaG86ev5hAidQvmOeETBqs7jm43K2F5/Ley3ytDtriImV6TpNiSg==
+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 "^3.3.1"
+ nanoid "^3.3.6"
  picocolors "^1.0.0"
  source-map-js "^1.0.2"