Implement Attachments

[KarstenSchulz]

Create an API to attach audio or image files. From https://www.2doapp.com/kb/article/url-schemes.html:

picture: (iOS 3.8.3+, Mac 2.2.2+) This can be one of two things. If the value passed is ‘lastphoto’ (iOS only), 2Do will grab the most recent photo placed on your camera roll. If the pass value is a base64 encoded string, 2Do will convert it into an image and use that as the attachment.

audio: (iOS 3.8.3+, Mac 2.2.2+) Provide a base64 encoded audio attachment