feat: Add Adventure docs

[Strokkur424]

Redo of #569.

Differences between the current Kyori docs:

• Whilst the index pages exist path wise, they aren't directly accessible via the side bar. I am not sure how, or even if it is possible, to do that, so that's something for scorp to fix 😀.
• On a few of the serialiser pages (only on those where a dependency is displayed via the <AdventureDependency /&mt; tag, I had to add an extra code block displaying the way to retrieve an instance, as without a code block, the imported code block is not rendered correctly. This seems to be an Astro/expressive-code related bug, but I still needed a non-intrusive workaround. reported, waiting for fix
• On the MiniMessage format page, certain screenshots are aligned/sized slightly differently than in the Kyori ones. If desired, I can try to conclude more parity, but that wasn't a priority when I initially wrote the docs.

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TODO:

• Add slugs to pages
• Inline code block syntax highlighting (low priority)

Blocked on:

• Code component does not display correctly with emitExternalStylesheet: false withastro/starlight#3207

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