Link preview generation with new link preview property

[Björn Bidar]

Hello,

I have a few question regarding the new link preview handler property
added recently. I ported the org-remoteimg package to it which was quite
easy, much cleaner with the new property.

The PR do port the package to this new handler property:
https://github.com/gaoDean/org-remoteimg/pull/4

However it left me with a few questions:
- Who is supposed to take care of the scaling/width of the preview
  image, the handler or the caller of the handler?
- When calling the link preview function for a description with prefix
  argument 1 I noticed that it doesn't get the contents of the
  description.
  Why is that? In this instance the link looked like this:
  
[[https://stable.melpa.org/#/rpm-spec-mode][file:https://stable.melpa.org/packages/rpm-spec-mode-badge.svg]]

Thanks have a great day,

Björn