Ensure pop-out windows / Obsidian 0.15.0 compatibility

[Taitava]

Another discussion (#323) already contains stuff about ensuring compatibility between SC and Obsidian 0.15.x / Code Mirror 6.0, but I found out that there's also another upgrade guide for plugin developers in Obsidian's forums: https://forum.obsidian.md/t/plugin-developers-how-to-update-your-plugin-to-support-pop-out-windows/40228

TODO: Check the guide and see if there's anything in the code that needs updating, and list here. I assume there is not much to update, but will see.