feat!: migrate to shiki v1

[antfu]

This PR removes highlighter: shikiji support. Use highlighter: shiki instead. Breaking changes between shiki v0.x to shiki v1 applies. For example, if you are using loadTheme in shiki setup, change it to manual fs reads instead.

This PR also improves the TwoSlash support by using floating-vue

[John98Zakaria]

I was using shikji as a highlighter as it had a nicer theme.
Do you happen to know how I can get the theme back in Shiki ?

Before (transparent background)

After

Update for anyone crying about their lost styles, add this to your styles.css and you are back in business

/* Shikiji */
html.dark .shiki {
  color: var(--shiki-dark, inherit);
  background: var(--shiki-dark-bg, inherit);
  --twoslash-popup-bg: var(--shiki-dark-bg, inherit);
}

html.dark .shiki span {
  color: var(--shiki-dark);
}

html:not(.dark) .shiki {
  color: var(--shiki-light, inherit);
  background: var(--shiki-light-bg, inherit);
  --twoslash-popup-bg: var(--shiki-light-bg, inherit);
}

html:not(.dark) .shiki span {
  color: var(--shiki-light);
}