time to read component

[beforan]

✨ Feature

PR Description

This PR adds the DocMetadata wrapper component for displaying document metadata at the top of a document page.

It also adds the TimeToRead component, included in DocMetadata as the first example of a metadata component.

Usage

1. Add <DocMetadata /> at the top of your .mdx pages to include any metadata components
2. Add suitable metadata to your document's frontmatter, e.g.

---
readingTime: PT15M
---

import {DocMetadata} from "@components/doc-metadata/DocMetadata"
<DocMetadata/>

# My Docs
...

For readingTime the format is ISO 8601 Duration.