It's useful, when developing new level gen techniques, to be able to
specially mark certain areas of the map during devlopment. This adds a
Marker entity type, which renders as a red X on the map and provides a
programmable description when examined. In the future it'll probably be
nice to toggle markers on/off just like we do with revealAll, but for
now it'll be fine to just remove the code to render them like we do with
debug traces.
Change-Id: Ief5d090809a0a4cbcc28f90e4902a5e38d42eeb5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/724
Reviewed-by: glittershark <grfn@gws.fyi>
20bc4aa10d
