Renaming `transformInclude` to `when`

I think it will give another DX:

const plugin = defineUnplugin({
  name: 'my-first-unplugin',
  setup(options: UserOptions) {
    return {
      // webpack's id filter is outside of loader logic,
      // an additional hook is needed for better perf on webpack
      when (id) {
        return id.endsWith('.vue')
      },
      // just like rollup transform
      transform (code) {
        return code.replace(/<template>/, `<template><div>Injected</div>`)
      },
      // more hooks incoming
    }
  }
})

Also, filter could also work, feedback welcome @pi0 @danielroe @antfu

[pi0]

I think transformInclude or any name has transform inside shouldTransform makes better sense since goal is not solely a unified transformer.

[Atinux]

In that case if we need to keep transform as prefix, transformInclude looks best 😅 we