Add some base markdown styles

This is lighter-weight and arguably easier to configure that Tailwind's
typography plugin though I could switch to it at a later date if needed.

assets/css/components.pcss

@@ -1,3 +1,27 @@
-.visually-hidden {
-  @apply sr-only;
+@layer components {
+  .markdown {
+    * + * {
+      @apply mt-4;
+    }
+
+    h2 + * {
+      @apply mt-2;
+    }
+
+    h2 {
+      @apply mt-6;
+    }
+
+    ul {
+      @apply pl-6 list-disc;
+    }
+
+    li {
+      @apply mt-0;
+    }
+  }
+
+  .visually-hidden {
+    @apply sr-only;
+  }
 }