[DONE][Suggestion] Option to mark geoscape textures as ocean

[Cooper]

So the default single-colored ocean in geoscape is a bit boring.. Suggesting an option to allow modders to add different ocean textures, while still having the ocean being an ocean (no crash landed UFOs in the sea).

globe:
  textures:
    - id: 0
      isOcean: true # default false

[Meridian]

Done.

https://github.com/MeridianOXC/OpenXcom/commit/eb208210926aca2093cbdb12319c27f9220c2624