Adds Reference Overview Page

[brianjo]

This draft PR creates a home page for the Reference section of the React documentation. The purpose of this page is to provide a scannable overview of the documentation and make it easier for readers to get to the information they are looking for. The key feature is that it allows for the hooks section to be closed by default so the rest of the documentation is accessible from the Reference landing page.

The PR does the following.

• Creates a new overview page, which was renamed to index.md
• Renames the current index.md file to hooks.md
• Updates the left navigation to include the new page at the top.

[github-actions]

Size changes

📦 Next.js Bundle Analysis for react-dev

This analysis was generated by the Next.js Bundle Analysis action. 🤖

One Page Changed Size

The following page changed size from the code in this PR compared to its base branch:

Page	Size (compressed)	First Load
/[[...markdownPath]]	78.92 KB (🟡 +15 B)	182.66 KB

Details

Only the gzipped size is provided here based on an expert tip.

First Load is the size of the global bundle plus the bundle for the individual page. If a user were to show up to your website and land on a given page, the first load size represents the amount of javascript that user would need to download. If next/link is used, subsequent page loads would only need to download that page's bundle (the number in the "Size" column), since the global bundle has already been downloaded.

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Next to the size is how much the size has increased or decreased compared with the base branch of this PR. If this percentage has increased by 10% or more, there will be a red status indicator applied, indicating that special attention should be given to this.

[lunaleaps]

lgtm! I tried to see if there was a way for git to mark the move, but it seems to be more Github auto-detection?