loader.js

const fm = require('front-matter')

module.exports = async function(content) {
  const callback = this.async()

  const output = fm(content)
  const attributes = []
  for (const [key, value] of Object.entries(output.attributes)) {
    attributes.push(`export const ${key} = ${JSON.stringify(value)}`)
  }

  const results = `${output.body}\n\n${attributes.join('\n\n')}\n`

  return callback(null, results)
}