Allow attachments to be send with the mail

[arnelap]

It's been requested to allow email attachments (instead of a link). Maybe just via a filter hook is fine.

[dannyvankooten]

After 0c72a670d4d63de86c17991c5e1dcd5b0855f559 one can use the following snippet to show a direct link to the uploaded file. Not yet attachments, but it's a step towards that direction.

add_filter('hf_file_upload_use_direct_links', '__return_true');

Hesistant to add attachment because spam scores will suffer and I reckon lots of people have shitty spam scores for their shared hosting powered emails anyway.