fix: does not import every langs and themes

[Barbapapazes]

related to #92 and nuxt/content#2422

I'm trying to avoid the bundling of every themes and langs becuase it makes the shikijs folder, in node_modules, of NItro too heavy.

But, even this PR, without loading a theme nor langs, it bundles all of shikijs.

@antfu or @pi0, did you know you we could avoid that?

[pi0]

This is a nice PR but i'm afraid disabling them by default might not be best decition as this limitation mainly affects edge deployments.

Maybe we can make it behind a syntaXhighlight: 'shiki-lite' mode configuration and auto enable for edge deployments in order to reduce size? (IMO a disabled also would really make sense to allow reducing deployment size when runtiume highlight is not necessary)

[antfu]

To reduce the bundle size, you need to avoid importing shikiji main entry. Instead, you will need to compose it from shikiji/core shikiji/wasm shikiji/langs/xxx shikiji/themes/xxx and only import what you need staticially.

If we ever need dynamic languages/themes support that means we need to bundle all languages regardlessly.

[farnabaz]

Closing in favor of #129