Allow asides titles to contain markdown formatting

[essential-randomness]

Description

• Closes Support code blocks in Aside titles #1915 and Tip's titles are truncated when using inline code docs#8711
• What does this PR change?

Fixes a bug where aside titles would get cut out if any markdown formatting was added in them.

Markdown of aside with formatting:

Before the fix

After the fix

I took the liberty to add mdast-util-to-string as a dependency. You already had hast-util-to-string so I assumed this would be fine and better than writing bespoke code to handle nested formatting. Let me know if you want me to remove it.

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Latest commit: 7fc5570

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@astrojs/starlight	Patch

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[HiDeoo]

Thanks a lot for your contribution 🙌

I did not yet dive in detail into the changes, altho they seems pretty straightforward at first glance (except maybe the lock file changes, looks like quite a few deps got updated).

One thing I'd like to point out and discuss before moving forward is the <Aside/> component. This would be a difference in behavior/features between the directive syntax and the component syntax.

I guess there are several possibilities to handle this, e.g. only support this for the directive syntax like in the current implementation, or also support it for the component syntax. I think I'm personally leaning towards the latter, but I'd like to hear people's opinions on this.

[delucis]

Thanks @essential-randomness! This looks great.

Regarding @HiDeoo’s question about what to do about <Aside>, that’s a great question!

My initial thought was “we can just require HTML there and use set:html” — i.e. usage like

<Aside title="Custom <code>code</code> label">

But then we’ll still need to strip out the HTML for the aria-label. That may still be preferable to supporting full-on Markdown rendering there though?

Also curious whether people think it’s OK to merge this before fixing support in <Aside>?

[HiDeoo]

That may still be preferable to supporting full-on Markdown rendering there though?

I think so, this would align with the banner behavior for example and would be way more practical than let's say a slot.

Also curious whether people think it’s OK to merge this before fixing support in <Aside>?

I personally think it's fine to merge this first, my comment was more about pointing out the potential difference and discuss it rather than having it block this PR.

[delucis]

Thanks again for the PR @essential-randomness! Happy with this and then we can think about how to tackle <Aside> support in a similar vein if and when it is needed.