Prepare dark theme, add pricing page

tailwind.config.js

@@ -8,7 +8,12 @@ module.exports = {
     './components/**/*.{js,ts,jsx,tsx}',
   ],
   theme: {
-    extend: {},
+    extend: {
+      transitionProperty: {
+        'width': 'width',
+        'spacing': 'margin, padding',
+      },
+    },
   },
   plugins: [
     createThemes({
@@ -21,5 +26,9 @@ module.exports = {
         foreground: '#ededed',
       },
     }),
+    require('tailwindcss/plugin')({
+      darkMode: 'class',
+    }),
   ],
+  darkMode: 'class',
 }