Add and configure Tailwind CSS

Add and configure Tailwind CSS within the project, including adding npm
scripts for compiling the CSS, configuring purge settings, and adding
the `cssnano` library for minifying the CSS (which is run for production
builds).

postcss.config.js

@@ -0,0 +1,8 @@
+module.exports = {
+    plugins: [
+        require('tailwindcss'),
+        ...process.env.NODE_ENV === 'production'
+            ? [require('cssnano')]
+            : []
+    ]
+}