Low-friction artist pipeline

[ViMaSter]

Description

Writers can already test their scripts without using the Unity editor, let's do the same for artists.

Acceptance Criteria

This story will be finished when

• pressing a specific combination of keys in development builds launches an artist test scene
  • runs a dialogue script, with three layers of sprites
  • layer A in the background
  • layer B in the middle
  • layer C in the foreground
  • after launching the scene, a file explorer window opens a directory containing a file for each layer
  • the scene is reloaded if any of these three files changes
• the exact combination of keys isn't defined yet; feel free to discuss (or whoever implements can just pick one)
• documentation for it is added to the GitHub Wiki

[notexplosive]

Is this a dupe of https://github.com/Studio-Lovelies/GG-JointJustice-Unity/issues/224?