[New Feature] Add `AmbientSound` to ObjectTypes.

[CCHyper]

Description:

Red Alert 2 introduced an INI key for ObjectTypes called AmbientSound=, this played the defined sound while this object exists on the game map.

Possible Implementation:

Copy the feature as-is from Red Alert 2.

For Discussion:

Is AmbientSound played only to the player or all players within the game?