move nodes and marks to a separate folder, add missing extensions

docs/src/docPages/api/nodes/blockquote.md

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+# Blockquote
+
+The Blockquote extension enables you to use the `<blockquote>` HTML tag in the editor. This is great – you might have guessed – to use quotes in the editor.
+
+Type <code>>&nbsp;</code> at the beginning of a new line and it will magically transform to a blockquote.
+
+## Installation
+```bash
+# with npm
+npm install @tiptap/extension-blockquote
+
+# with Yarn
+yarn add @tiptap/extension-blockquote
+```
+
+## Settings
+| Option | Type   | Default | Description                                  |
+| ------ | ------ | ------- | -------------------------------------------- |
+| class  | string | –       | Add a custom class to the rendered HTML tag. |
+
+## Commands
+| Command    | Options | Description                   |
+| ---------- | ------- | ----------------------------- |
+| blockquote | —       | Wrap content in a blockquote. |
+
+## Keyboard shortcuts
+* Windows/Linux: `Control`&nbsp;`Shift`&nbsp;`9`
+* macOS: `Cmd`&nbsp;`Shift`&nbsp;`9`
+
+## Source code
+[packages/extension-blockquote/](https://github.com/ueberdosis/tiptap-next/blob/main/packages/extension-blockquote/)
+
+## Usage
+<demo name="Extensions/Blockquote" highlight="3-5,17,36" />