beta 16 - Laravel 8 fix

[eddiewebb]

Fixes #12 for Beta 16

Changes proposed in this pull request: Instead of implementing mailer ourselves, this change updates to use Laravel 8.x mailmanager, and get a modified mailer instance from it.

Reviewers should focus on: THere was previously a custom fof Mailer.php that extended laravel's Mailer. Please confirm we're properly registering that instance in the manager to return later.

Screenshot

Confirmed

• [x] Frontend changes: tested on a local Flarum installation.
• [ ] Backend changes: tests are green (run composer test).

hmm

 composer test

  [Symfony\Component\Console\Exception\CommandNotFoundException]  
  Command "test" is not defined. 

[imorland]

Thank you very much for this @eddiewebb 👍

I'll review this later today/tomorrow, I'll come back to you if I have any questions!