Update dependency cssnano to v7

packages/webapp/public/98.css/package.json

@@ -27,7 +27,7 @@
   "homepage": "https://github.com/jdan/98.css",
   "devDependencies": {
     "chokidar": "^3.3.1",
-    "cssnano": "^5.0.1",
+    "cssnano": "^7.0.0",
     "dedent": "^0.7.0",
     "ejs": "^3.0.2",
     "gh-pages": "^2.2.0",