Support Email Attachments

[NeonDaniel]

Email attachments should be (optionally) supported for backends (like Neon) that can handle them. Default behavior will need to be defined if a backend doesn't support attachments.. Some possibilities:

• Raise an exception
• Log an exception and send the email with no attachments
• Try appending attachment contents as text to the email body (warn/fail on binary files)

ovos-backend-client/ovos_backend_client/api.py

Line 236 in 8b95d72

def send_email(self, title, body, sender):

In Neon:
https://github.com/NeonGeckoCom/neon-skill-utils/blob/dev/neon_utils/skills/neon_skill.py#L314-L329