Additional export options / Multiple file save

There is an option for exporting multiple tags as a sprite sheet with rows for each tag, but I wanted to suggest to add exporting options to save multiple files with different specific names/frames/tags. Basically a batch save.

I usually working with one Aseprite file per character and there are a ton of different animations in there. So when it comes to exporting everything it can be kinda frustrating to split and rename everything separately as you need.

The CLI export options already support this using toggles (e.g. --split-tags) and name templates, it would be nice to have those in the GUI, using the same templates and perhaps checkboxes for the various toggles.