function isFileNameBinary (filepath) {
  const ext = path.extname(filepath)
  if (binextensions.includes(ext)) return true
  if (textextensions.includes(ext)) return false
  // dont know
}
Guesses if the file is binary based on its path.
Returns 'undefined' if no guess can be made.
@param {string} filepath
@returns {boolean | undefined}