Support importing modules from outside of the root emails/ folder

[callumdmay]

Hey guys, really love this package, it's so useful especially with the tailwind support. I'm trying to import a file from outside the emails/ folder into one of my email templates, however when I go to preview it, next.js is throwing an error:

Module not found: Can't resolve 'src/util/file.ts'

Looks like it might be because of how the next.js server instance is configured to resolve modules:

Import trace for requested module:
./emails/ lazy ^\.\/.*$ namespace object
./src/pages/preview/[slug].tsx

I can fix this by simply moving file.ts to emails/file.ts but that isn't ideal because file.ts is used a utility file used elsewhere

[Bugs5382]

I had to keep my additional folders for helpers, etc. inside the emails folder.

emails
- helpers

As long as it's a valid react element, it will work.

[callumdmay]

This does work, but ideally I would like to avoid copying my helper util files into the email folder