Fix warning logs when building the app using svelte-email-tailwind

[NanezX]

Hello @steveninety, this a great package and awesome work!

I know this issue is not a huge emergency or critical error, but I would like to get ride of the warning logs that we can see when building the app that use the package.

• The first one is:
  This is due that the recommended way is to use the exports condition on the package.json. Of course, this is also updated on the @sveltejs/package that help us to packaging, and correctly set the right exports to remove that warning.

3:25:31 PM [vite-plugin-svelte] WARNING: The following packages have a svelte field in their package.json but no exports condition for svelte.

svelte-email-tailwind@2.0.1

Please see https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/faq.md#missing-exports-condition for details.

• The second one:
  This one is due the package pretty is not being used on the package itself, so display this warning. Maybe this one is something that you added for your personal use (idk), but of course can be installed separability.

"default" is imported from external module "pretty" but never used in "node_modules/svelte-email-tailwind/index.js".

I did a fork from the repository to see what I can do on this.

The main concern is that I do not have too much experience using @sveltejs/package, but I'll have to update it and do the migration based on the guide. Unless we can do it just using the current version

[NanezX]

I submitted the PR #18.

Hope can help or give a starting point :)

[steveninety]

Should be solved in v2.1.0!