function sanitizeFilePath (filePath) {
  return filePath.replace(/^\/+/, '')
}
Removes the leading slash from a filePath if it exists.

If the filePath has a leading slash, s3 interprets that leading slash as an unnamed top-level directory that
all other files nest under; this causes the static website to infinitely redirect.

@param {string} filePath
@returns {string} File path without a leading slash