docs: add descriptions to all extensions

docs/api/marks/bold.md

@@ -1,3 +1,7 @@
+---
+description: Make your text bold and let it stand out.
+---
+
 # Bold
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-bold.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-bold)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-bold.svg)](https://npmcharts.com/compare/@tiptap/extension-bold?minimal=true)

docs/api/marks/code.md

@@ -1,3 +1,7 @@
+---
+description: Developers love to add some inline code to their texts.
+---
+
 # Code
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-code.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-code)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-code.svg)](https://npmcharts.com/compare/@tiptap/extension-code?minimal=true)

docs/api/marks/highlight.md

@@ -1,3 +1,7 @@
+---
+description: Make it look nerdier with some colorful text highlights.
+---
+
 # Highlight
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-highlight.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-highlight)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-highlight.svg)](https://npmcharts.com/compare/@tiptap/extension-highlight?minimal=true)

docs/api/marks/italic.md

@@ -1,3 +1,7 @@
+---
+description: Helps to emphasize your text, doesn’t bring you closer to Italy though.
+---
+
 # Italic
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-italic.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-italic)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-italic.svg)](https://npmcharts.com/compare/@tiptap/extension-italic?minimal=true)

docs/api/marks/link.md

@@ -1,3 +1,7 @@
+---
+description: Link it, link it good, link it real good (and don’t forget the href).
+---
+
 # Link
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-link.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-link)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-link.svg)](https://npmcharts.com/compare/@tiptap/extension-link?minimal=true)

docs/api/marks/strike.md

@@ -1,3 +1,7 @@
+---
+description: Cut through the words you wrote, if you’re too afraid to delete it.
+---
+
 # Strike
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-strike.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-strike)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-strike.svg)](https://npmcharts.com/compare/@tiptap/extension-strike?minimal=true)

docs/api/marks/subscript.md

@@ -1,3 +1,7 @@
+---
+description: Write slightly below the the normal line, to show you’re unique.
+---
+
 # Subscript
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-subscript.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-subscript)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-subscript.svg)](https://npmcharts.com/compare/@tiptap/extension-subscript?minimal=true)

docs/api/marks/superscript.md

@@ -1,3 +1,7 @@
+---
+description: Write slightly above the the normal line, to show you’re just next level.
+---
+
 # Superscript
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-superscript.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-superscript)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-superscript.svg)](https://npmcharts.com/compare/@tiptap/extension-superscript?minimal=true)

docs/api/marks/text-style.md

@@ -1,3 +1,7 @@
+---
+description: Useless extension, just adds <span> tags (required by other extensions though).
+---
+
 # TextStyle
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-text-style.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-text-style)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-text-style.svg)](https://npmcharts.com/compare/@tiptap/extension-text-style?minimal=true)

docs/api/marks/underline.md

@@ -1,3 +1,7 @@
+---
+description: Add a line below your text to make it look more … underlined.
+---
+
 # Underline
 [![Version](https://img.shields.io/npm/v/@tiptap/extension-underline.svg?label=version)](https://www.npmjs.com/package/@tiptap/extension-underline)
 [![Downloads](https://img.shields.io/npm/dm/@tiptap/extension-underline.svg)](https://npmcharts.com/compare/@tiptap/extension-underline?minimal=true)