improve extensions documentation

docs/src/docPages/api/extensions/horizontal-rule.md

@@ -0,0 +1,57 @@
+# HorizontalRule
+Enables you to use the `<hr>` HTML tag in the editor.
+
+## Options
+*None*
+
+## Commands
+| Command | Options | Description |
+| ------ | ---- | ---------------- |
+| horizontal_rule | none | Create a horizontal rule. |
+
+## Keybindings
+*None*
+
+## Usage
+```markup
+<template>
+  <div>
+    <editor-menu-bar :editor="editor" v-slot="{ commands, isActive }">
+      <button type="button" @click="commands.horizontal_rule">
+        Horizontal Rule
+      </button>
+    </editor-menu-bar>
+
+    <editor-content :editor="editor" />
+  </div>
+</template>
+
+<script>
+import { Editor, EditorContent, EditorMenuBar } from 'tiptap'
+import { HorizontalRule } from 'tiptap-extensions'
+
+export default {
+  components: {
+    EditorMenuBar,
+    EditorContent,
+  },
+  data() {
+    return {
+      editor: new Editor({
+        extensions: [
+          new HorizontalRule(),
+        ],
+        content: `
+          <p>Some text.</p>
+          <hr />
+          <p>Text again.</p>
+        `,
+      }),
+    }
+  },
+  beforeDestroy() {
+    this.editor.destroy()
+  }
+}
+</script>
+```