Feature request: Image folding support (fold data: URL)

This is a follow-up to:
https://github.com/ajaxorg/ace-builds/issues/147#issuecomment-449745497

I use the CSS suggested in that comment, but to make image folding work, I still need the patches as described in
https://github.com/ajaxorg/ace-builds/issues/147#issuecomment-448415677

I've just tried again with the latest release 1.4.12.

The background to this request is the following: As you are aware, Ace is embedded into the Thunderbird add-on ThunderHTMLedit. Each time a new version of add-on is uploaded to addons.thunderbird.net, it needs to go through a review process. The reviewers there prefer to approve a "stock standard" 3rd-party library and not a patched one. Also for me it would be easier to move to new versions if I didn't have to patch them.

So please let me know if you would consider this request, and if so, whether I can help in any form.