fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-ISAACSBRACEEXPANSION-15208653
- https://snyk.io/vuln/SNYK-JS-GLOB-14040952

Author: snyk-bot

package.json

@@ -73,7 +73,7 @@
   },
   "homepage": "https://gethinode.com",
   "dependencies": {
-    "@fullhuman/postcss-purgecss": "^7.0.2",
+    "@fullhuman/postcss-purgecss": "^8.0.0",
     "autoprefixer": "^10.4.21",
     "cssnano": "7.1.1",
     "cssnano-preset-advanced": "^7.0.10",