[5.3] Send multipart email notification

[tillkruss]

It would be nice if Laravel would send a plain text alternative alongside the HTML email notifications out of the box. Reasons for that are:

• Improves the spam score
• Some email clients/apps still can’t handle HTML
• Some people prefer viewing emails as plain text

Since calling php artisan vendor:publish is necessary anyhow to add the new plain text template file, I also went ahead and changed the resource directory structure from:

notifications/email.blade.php

To:

notifications/email/html.blade.php
notifications/email/text.blade.php

If that's too much of a breaking change, we could do this:

notifications/email.blade.php
notifications/email-plain.blade.php

Feedback appreciated 😀

[taylorotwell]

I would go with the non-breaking change method.

[tillkruss]

Done.

php artisan vendor:publish is still necessary, but users who customized their email.blade.php file won't have to move it.

[taylorotwell]

Thanks. Can you send a docs PR?

[tillkruss]

Sure.

laravel/docs#2581