add Dark Halls map

[lazylier]

I haven't been able to play test this, so it might not work right.

[a-bad-dev]

Haven't fully tested it yet but here are a few issues:

1. The barrier is visible in the screenshot, remove the barriers before taking the screenshot.
2. Got an error involving chest zones while loading the map, and some nodes behaved like chests (see screenshot), the chest zone(s) need adjustment.

The map is unlike any other map I've seen (excepting maybe a mix of Water Academy's tunnels and the underworld's theme in Titanomachy: Aftermath)

[lazylier]

I tried saving again. It works now for me.