Support Shiki's defaultColor option in Astro's <Code/> component

[ARipeAppleByYoursTruly]

Body

Summary

Make Astro's <Code/> component support Shiki's defaultColor option for better control on dual/multiple themes styling.

Background & Motivation

By default, Shiki uses CSS' !important flag to override the default theme's styles to another. This approach introduces a problem when the user wants to "reverse" the default theme, ie. apply dark theme as default, as !important ignores cascading.

In order to solve this problem, or avoid using !important in general, the defaultColor option should be set explicitly, as Shiki defaults defaultColor to "light", detailed in Shiki docs. But Astro's <Code/> component doesn't expose defaultColor, and so here we are.

I'm aware that Expressive Code has solved this problem, but it would be nice to give the user another option to work with.

Goals

• Add defaultColor prop to Astro's <Code/> component, its value will be passed to highlighter.codeToHtml()
• Make defaultColor behave like Shiki's for consistency

Example

I've tried implementing it and seems successful in this repo. Changes I've made are in the node_modules - modified files directory.

[ARipeAppleByYoursTruly]

Bumping for visibility as this got stale

[ematipico]

This feature is small. If you want, try to send a PR. :)

To me, it seems a reasonable request

[bluwy]

There's also an issue opened in Astro respectively withastro/astro#11238, but that's for the shikiConfig, not <Code />. However, if we do support the option, we can (and probably should) support in both places at once.

Definitely welcome a PR though.

[ARipeAppleByYoursTruly]

I'll try making a PR after withastro/astro#11238's PR have been merged, thanks for the green light

[bluwy]

As a heads up, we usually merge feature PRs for minors every 2 weeks on Wednesday (the next is Wednesday next week). So if you'd like to have the feature in soon, it may be good to create a PR based on withastro/astro#11238 so it's also ready during then, or we'd have to wait another 2 weeks if the PR comes later.

[ematipico]

@bluwy I think we will skip next week. There's a thread on discord to talk about it