perf: modular sass architecture (#2052)

- Modularized the Sass architecture to enhance code maintainability and reduce the output file size
- Replaced deprecated `@import` with `@use` / `@forward`

purgecss.js

@@ -0,0 +1,30 @@
+const fs = require('fs').promises;
+const { PurgeCSS } = require('purgecss');
+const DIST_PATH = '_sass/vendors';
+const output = `${DIST_PATH}/_bootstrap.scss`;
+
+const config = {
+  content: ['_includes/**/*.html', '_layouts/**/*.html', '_javascript/**/*.js'],
+  css: ['node_modules/bootstrap/dist/css/bootstrap.min.css'],
+  keyframes: true,
+  variables: true,
+  // The `safelist` should be changed appropriately for future development
+  safelist: {
+    standard: [/^collaps/, /^w-/, 'shadow', 'border', 'kbd'],
+    greedy: [/^col-/, /tooltip/]
+  }
+};
+
+function main() {
+  fs.rm(DIST_PATH, { recursive: true, force: true })
+    .then(() => fs.mkdir(DIST_PATH))
+    .then(() => new PurgeCSS().purge(config))
+    .then((result) => {
+      return fs.writeFile(output, result[0].css);
+    })
+    .catch((err) => {
+      console.error('Error during PurgeCSS process:', err);
+    });
+}
+
+main();