Add new function to enable/disable preview of map to lua

[ottml]

We need lua functionality to have possibility to disable the map preview for missions. So the user can not see the map in advance.

[Flow86]

can we perhaps instead of not showing any map if preview is disabled, showing some "Hidden" map view, don't know if we can generate a preview of something like that?

[Flamefire]

can we perhaps instead of not showing any map if preview is disabled, showing some "Hidden" map view, don't know if we can generate a preview of something like that?

Maybe some placeholder graphics. Not sure if it is worth the effort. But if e.g. @Spikeone wants to provide an image @ottml likes I'm fine with it. Otherwise I'd just keep the current state of the PR

[Spikeone]

@Flamefire I'd to this without a graphic. Can't we just add a gray area (like for player colors) and either use a scaled up '?' or simply write "no preview" or something alike in that area?

[Flow86]

Can't we just add a gray area (like for player colors) and either use a scaled up '?' or simply write "no preview" or something alike in that area?

thats a good idea

[ottml]

[Spikeone]

hey @ottml just asking since I've seen something alike in the campagin.lua - wouldn't it be great to set some kind of preview graphic - so one could for example set the SETUP810.LBM in order to hint, that this is winter map.