async function readAsset (drive, pathname) {
  if (pathname.endsWith('.ico')) {
    let data = await drive.pda.readFile(pathname, 'binary')
    // select the best-fitting size
    let images = await ICO.parse(data, 'image/png')
    let image = images[0]
    for (let i = 1; i < images.length; i++) {
      if (Math.abs(images[i].width - IDEAL_FAVICON_SIZE) < Math.abs(image.width - IDEAL_FAVICON_SIZE)) {
        image = images[i]
      }
    }
    let buf = Buffer.from(image.buffer)
    return `data:image/png;base64,${buf.toString('base64')}`
  } else {
    let data = await drive.pda.readFile(pathname, 'base64')
    return `data:${mime.lookup(pathname)};base64,${data}`
  }
}
Reads the asset file as a dataurl
- Converts any .ico to .png
@param {DaemonHyperdrive} drive
@param {string} pathname
@returns string The asset as a data URL