docs(v2): Reorganize/split the guides doc sections (#3975)

* docs reorg

* refactor docs/markdown features section

* fix broken links after docs refactor

website/docs/guides/markdown-features/markdown-features-plugins.mdx

@@ -0,0 +1,78 @@
+---
+id: plugins
+title: Plugins
+description: Using MDX plugins to expand Docusaurus Markdown functionalities
+slug: /markdown-features/plugins
+---
+
+You can expand the MDX functionalities, using plugins.
+
+Docusaurus content plugins support both [Remark](https://github.com/remarkjs/remark) and [Rehype](https://github.com/rehypejs/rehype) plugins that work with MDX.
+
+## Configuring plugins
+
+An MDX plugin is usually a npm package, so you install them like other npm packages using npm.
+
+First, install your [Remark](https://github.com/remarkjs/remark/blob/main/doc/plugins.md#list-of-plugins) and [Rehype](https://github.com/rehypejs/rehype/blob/main/doc/plugins.md#list-of-plugins) plugins.
+
+For example:
+
+```bash npm2yarn
+npm install --save remark-images
+npm install --save rehype-truncate
+```
+
+Next, import the plugins:
+
+```js
+const remarkImages = require('remark-images');
+const rehypeTruncate = require('rehype-truncate');
+```
+
+Finally, add them to the `@docusaurus/preset-classic` options in `docusaurus.config.js`:
+
+```js {10,11} title="docusaurus.config.js"
+module.exports = {
+  // ...
+  presets: [
+    [
+      '@docusaurus/preset-classic',
+      {
+        docs: {
+          sidebarPath: require.resolve('./sidebars.js'),
+          // ...
+          remarkPlugins: [remarkImages],
+          rehypePlugins: [rehypeTruncate],
+        },
+      },
+    ],
+  ],
+};
+```
+
+## Configuring plugin options
+
+Some plugins can be configured and accept their own options. In that case, use the `[plugin, pluginOptions]` syntax, like so:
+
+```jsx {10-13} title="docusaurus.config.js"
+module.exports = {
+  // ...
+  presets: [
+    [
+      '@docusaurus/preset-classic',
+      {
+        docs: {
+          sidebarPath: require.resolve('./sidebars.js'),
+          // ...
+          remarkPlugins: [
+            plugin1,
+            [plugin2, {option1: {...}}],
+          ],
+        },
+      },
+    ],
+  ],
+};
+```
+
+See more information in the [MDX documentation](https://mdxjs.com/advanced/plugins).