Invalid escape sequence error on build

[merih]

Extension authors cannot use String.raw or any other template string tags that accept unexpected escape sequences in babel v6.

e.g.

Module build failed: SyntaxError: Invalid escape sequence in template (2:24)

  1 |
> 2 |             String.raw`\u`;
    |                         ^
  3 |

Apparently this is fixed in babel v7.x: babel/babel#8502