feat: add Tailwind CSS and PostCSS configuration

- Created postcss.config.js to configure PostCSS with Tailwind CSS and Autoprefixer.
- Updated svelte.config.js to enable PostCSS preprocessing.
- Added tailwind.config.js for Tailwind CSS configuration.
- Updated yarn.lock to include new dependencies for Tailwind CSS, PostCSS, and related plugins.

esbuild.config.js

@@ -1,4 +1,5 @@
 const fs = require("fs")
+const postcssPlugin = require("esbuild-postcss")
 
 const resolvePlugin = {
     name: "resolvePlugin",
@@ -54,7 +55,7 @@ const options = {
     minify: process.argv[2] == "build",
     bundle: true,
     splitting: false,
-    plugins: [esbuildSvelte, resolvePlugin],
+    plugins: [postcssPlugin(), esbuildSvelte, resolvePlugin],
     loader: {
         ".woff2": "file",
         ".woff": "file",