dev: use cssnano, postcss, postcss-cli and css-declaration-sorter packages for more control over minification

dev: exclude some files
dev: sort declarations alphabetically during minification

postcss.config.js

@@ -0,0 +1,22 @@
+const cssDeclarationSorter = require('css-declaration-sorter');
+const cssnano = require('cssnano');
+
+module.exports = {
+	plugins: [
+		cssDeclarationSorter({
+			keepOverrides: true,
+			order: (a, b) => {
+				const aVar = a.startsWith('--');
+				const bVar = b.startsWith('--');
+
+				if (aVar && !bVar) return -1;
+				if (!aVar && bVar) return 1;
+
+				return a.localeCompare(b);
+			},
+		}),
+		cssnano({
+			preset: 'default',
+		}),
+	],
+};