Add URL Image to PDF Template

@claudiovalverde Awesome idea! Could you share with me what processes do you see this feature being very useful? 

We have some processes that collect in attachment fields pictures of off-site services and we need to prepare a report with these pictures to send to some stakeholders. We know that is possible to do that adding that pictures at a template email using dinamic fields and we already did that, but sometimes the primary contact with the clients is with WhatsApp. That way we need to create that reports in pdf automatically and send to the client using WhatsApp. 

@claudiovalverde Thank you for the additional info, that is very helpful. I see the benefit of allowing users to share pictures they collect across their process via the PDF file generated at the end of the process. I'll give some thought about it. 

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