[add] Astro.props added to config (withastro#1200)

Co-authored-by: Chris Swithinbank <[email protected]>

src/pages/en/reference/api-reference.md

@@ -80,6 +80,33 @@ const posts = await Astro.glob<Frontmatter>('../pages/post/*.md');
 </ul>
 ```
 
+### `Astro.props`
+
+`Astro.props` is an object containing any values that have been passed as [component attributes](/en/core-concepts/astro-components/#component-props). Layout components for `.md` and `.mdx` files receive frontmatter values as props.
+
+```astro {3}
+---
+// ./src/components/Heading.astro
+const { title, date } = Astro.props;
+---
+<div>
+    <h1>{title}</h1>
+    <p>{date}</p>
+</div>
+```
+
+```astro /title=".+"/ /date=".+"/
+---
+// ./src/pages/index.astro
+import Heading from '../components/Heading.astro';
+---
+<Heading title="My First Post" date="09 Aug 2022" />
+```
+
+📚 Learn more about how [Markdown and MDX Layouts](/en/guides/markdown-content/#frontmatter-layout) handle props.
+
+📚 Learn how to add [Typescript type definitions for your props](/en/guides/typescript/#component-props).
+
 #### Astro Files
 
 Astro files have the following interface: