Adjust some heading styles and code blocks higlighting

[100gle]

What kind of changes does this PR include?

• New or updated content
• Something else!

Description

I adjust some heading styles and code block highlighting in guides/integrations-guide/cloudflare.mdx to make it be more readable.

Related Issue / Implementation PR

• Closes Issue #

[netlify]

✅ Deploy Preview for astro-docs-2 ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	e810033
🔍 Latest deploy log	https://app.netlify.com/sites/astro-docs-2/deploys/65139805b3a9cc00076c503f
😎 Deploy Preview	https://deploy-preview-4822--astro-docs-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[Genteure]

The file src/content/docs/en/guides/integrations-guide/cloudflare.mdx is pulled from the package README by a script running on GitHub Actions, as indicated at the start of the file:

# NOTE: This file is auto-generated from 'scripts/generate-integration-pages.ts'
#       and pulls content directly from the package’s README.
#       DO NOT MAKE EDITS TO THIS FILE DIRECTLY, THEY WILL BE OVERWRITTEN!
#       For corrections, please edit the package README at
#       https://github.com/withastro/astro/tree/main/packages/integrations/cloudflare/

Please close this PR and reopen another in https://github.com/withastro/astro

Another thing to consider is GitHub and npmjs.com (@astrojs/cloudflare) does not support expressive code. If the primary goal is highlight the differences then ```diff would be better because ```js ins={8} would get rendered like ```js. It's a tradeoff of UX between npmjs and astro doc site.

The @astrojs/cloudflare README already contains an "expressive code" code block.

docs/src/content/docs/en/guides/integrations-guide/cloudflare.mdx

Line 49 in ed9d8cc

```js ins={3, 6-7}

[Genteure]

After looking further into this, this PR would be a (partial) duplicate of withastro/astro#8654 as that PR also contains most of the changes made in this PR and more.

[alexanderniebuhr]

@100gle I've just added you as a co-author, to withastro/astro#8654. So you still have the contribution!