Convert to nextra 3

[tiffanyqi]

Honestly, I was looking into Nextra 3 because of breadcrumb linking, however it turns out that a couple of things are improved if we do it this way.

Pros

1. Increase in performance
2. Automatic breadcrumb linking (the first on the list)
3. Clearer code (example: sidebar icons moved directly to meta.ts rather than inside of theme.config)
4. Catches strange syntax things, for example weird image names

Before

After

Changes necessary to use Nextra 3

(this is mostly covered per commit):

1. Package changes is the main reason the file is so big
2. Next.config.js -> next.config.mjs
3. Convert all _meta.json files to _meta.ts
4. Convert Card and Tab to Cards.Card and Tabs.Tab

I'm mostly annoyed that there are so many changes that are not retroactive, but at least it wasn't too bad

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[myronkaifung]

We should prioritize fixing the code syntax highlighting since it makes the SDK pages a lot harder to read.

Not a blocker for this PR.