Feature Requst: Add APIs which can be used in build scripts for @import-meta-env/cli

[ylc395]

import { transform } from '@import-meta-env/cli' // or other package name

transform({ // async or sync
  path: './dist',
  env: {
    MY_ENV_VARIABLE: 'hello world'
  }
})

So that users can integrate this tool into build scripts.