Add support for inline images about lokole HOT 2 CLOSED

Some implementation pointers:

1. After the email has been converted to a domain object, use lxml to find all the image tags in the email['body'].
2. For each image tag, check if the src is a link. If so: use the requests library to fetch the image at the link; then use the base64 library to encode the image as a base64 data url. This will require taking a note of the mime type of the fetched image so that we can correctly formulate the data url prefix (data:image/png;base64,...).

from lokole.

Confirmed that this works in production.

from lokole.