Switch from Webpacker to cssbundling-rails, upgrade Tailwind

app/assets/stylesheets/components/buttons.css

@@ -0,0 +1,31 @@
+@layer components {
+  .btn {
+    @apply font-semibold rounded-md leading-none cursor-pointer
+           transition-colors duration-75 focus:outline-none focus:ring-4;
+  }
+
+  .btn-md {
+    @apply btn;
+    @apply py-2.5 px-5 shadow-md;
+  }
+
+  .btn-sm {
+    @apply btn;
+    @apply py-1 px-2 text-sm shadow-sm;
+  }
+
+  .btn-gray {
+    @apply bg-gray-100 hover:bg-gray-200
+           focus:ring-gray-300 focus:ring-opacity-75;
+  }
+
+  .btn-blue {
+    @apply bg-blue-500 hover:bg-blue-600 text-white
+           focus:ring-blue-400 focus:ring-opacity-75;
+  }
+
+  .btn-red {
+    @apply bg-red-600 hover:bg-red-700 text-white
+           focus:ring-red-500 focus:ring-opacity-75;
+  }
+}