fix(compare): support for Windows newlines and improve formatting

[erickzhao]

The main problem this fixes is that we're using \r\n for our major version release notes, so comparisons featuring a major version will be empty.

For example:
https://releases.electronjs.org/release/compare/v36.0.0-beta.9/v36.0.0

This PR makes the parsing more resilient by accepting both \n and \r\n.

The rest of the changes kind of follow from there to make the styling a bit better:

• Parsed ## headings are actually <h2> now so headings are semantic.
• Text size is made more uniform for headings within release notes.

[dsanders11]

I'm not sure this change is correct? The "Combined Release Notes" header is h3, so I think h4 here makes sense?

The headers go "Electron Releases" -> "Release Comparison" -> "Combined Release Notes"

[erickzhao]

Fixed in 9eb23f3 by shifting the rendered Markdown headings from the release notes by +2

[dsanders11]

Would adding levelShift: 2 to listMD also fix #155?

[MarshallOfSound]

Why did we drop the text size classes?

[erickzhao]

@MarshallOfSound some of the headings in the PR details have text-lg set to them so I wanted to make the heading level appearances more consistent:

release-status/app/routes/pr/details.tsx

Lines 263 to 266 in 566e0fa

	<h3 className="text-lg font-semibold text-[#2f3241] dark:text-white flex items-center gap-2">
	<GitBranch className="w-5 h-5" />
	Backport Information
	</h3>

With the PR in the state it is now, I don't actually think we need this change necessarily (headings generated by markdown-renderer in the compare view are h5 after 9eb23f3), but we could instead do the following to match the non-MD heading styles:

h1: text-xl
h2: text-xl
h3: text-lg
h4: text-lg
h5: text-base
h6: text-base

[erickzhao]

457021e