Add Falkland Islands map (#681)

## Description:
This PR adds the Falkland Islands map. It has 12 nations - most of the
regions of the islands. All use the Falkland Island flag as they don't
have their own.

## Please complete the following:

- [ ] I have added screenshots for all UI updates
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

<DISCORD USERNAME>
Nikola123

src/core/game/TerrainMapFileLoader.ts

@@ -44,6 +44,7 @@ const MAP_FILE_NAMES: Record<GameMapType, string> = {
   [GameMapType.FaroeIslands]: "FaroeIslands",
   [GameMapType.DeglaciatedAntarctica]: "DeglaciatedAntarctica",
   [GameMapType.EuropeClassic]: "EuropeClassic",
+  [GameMapType.FalklandIslands]: "FalklandIslands",
 };
 
 class GameMapLoader {