Merge pull request #470 from textpattern/dependabot/npm_and_yarn/cssnano-5.0.17

Bump cssnano from 5.0.16 to 5.0.17

Author: philwareham

package.json

@@ -13,7 +13,7 @@
     "@lodder/grunt-postcss": "3.1.1",
     "@squoosh/cli": "0.7.2",
     "autoprefixer": "10.4.2",
-    "cssnano": "5.0.16",
+    "cssnano": "5.0.17",
     "grunt": "1.4.1",
     "grunt-cli": "1.4.3",
     "grunt-concurrent": "3.0.0",