build: update postcss config

Author: mrholek

build/postcss.config.js

@@ -10,6 +10,7 @@ module.exports = context => {
   return {
     map: context.file.dirname.includes('examples') ? false : mapConfig,
     plugins: {
+      'postcss-drop-empty-css-vars': {},
       autoprefixer: {
         cascade: false
       },

package.json

@@ -52,7 +52,6 @@
     "lint": "npm-run-all --aggregate-output --continue-on-error --parallel js-lint css-lint lockfile-lint",
     "docs": "npm-run-all docs-build docs-lint",
     "docs-build": "hugo --cleanDestinationDir --printUnusedTemplates",
-    "docs-version": "hugo version",
     "docs-compile": "npm run docs-build",
     "docs-vnu": "node build/vnu-jar.js",
     "docs-lint": "npm run docs-vnu",
@@ -127,6 +126,7 @@
     "npm-run-all": "^4.1.5",
     "postcss": "^8.4.23",
     "postcss-cli": "^10.1.0",
+    "postcss-drop-empty-css-vars": "^0.0.0",
     "rollup": "^3.21.1",
     "rollup-plugin-istanbul": "^4.0.0",
     "rtlcss": "^4.1.0",