Refactor docs of packages

Author: wooorm

docs/_asset/index.css

@@ -912,6 +912,16 @@ button.success {
   background-color: var(--fg);
 }
 
+details {
+  border: 1px solid var(--gray-2);
+  padding: 1ex;
+  border-radius: 3px;
+}
+
+details[open] {
+  padding: calc(1em + 1ex);
+}
+
 @media (prefers-color-scheme: dark) {
   :root {
     --white: #f0f6fc;
@@ -1095,6 +1105,10 @@ button.success {
     border-color: var(--green-5);
     color: var(--white);
   }
+
+  details {
+    border-color: var(--gray-6);
+  }
 }
 
 @media (min-width: 22em) {

docs/docs/extending-mdx.mdx

@@ -104,8 +104,8 @@ You can use this template:
 ## Using plugins
 
 Where to pass plugins is encoded in their name: remark plugins go in
-[`options.remarkPlugins`][options-remark-plugins], rehype plugins
-in [`options.rehypePlugins`][options-rehype-plugins].
+`remarkPlugins` and rehype plugins go in `rehypePlugins` of
+[`ProcessorOptions`][processor-options].
 Those fields expect lists of plugins and/or of `[plugin, options]`:
 
 ```tsx
@@ -169,9 +169,7 @@ For info on the node types that represent MDX specific features, see
 
 [start]: /docs/getting-started/
 
-[options-remark-plugins]: /packages/mdx/#optionsremarkplugins
-
-[options-rehype-plugins]: /packages/mdx/#optionsrehypeplugins
+[processor-options]: /packages/mdx/#processoroptions
 
 [architecture]: /packages/mdx/#architecture