[beta] Ensure compat of Prettier and remark-header-custom-ids

[eps1lon]

Enables formatting docs pages with Prettier (handy syntax checker for code blocks).

Prettier currently applies the following diff to headings:

-## Add React in one minute {/*add-react-in-one-minute*/}
+## Add React in one minute {/* add-react-in-one-minute */}

These heading IDs were previously rejected since the leading/trailing spaces were converted to -. Now we just remove leading/trailing whitespace.

Applied Prettier to a page that showcases the change but doesn't have too many changes.

Example Page

[gaearon]

i feel like i appreciate the manual control over how the code is split by lines. e.g. for places where we highlight parts, it's pretty essential to have that control.

[github-actions]

Size Changes

📦 Next.js Bundle Analysis

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This PR introduced no changes to the javascript bundle 🙌