Have trains produce more gold (#1759)

During the play test, trains did not produce enough gold. So increase
gold, and give 4x bonus for allies.

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I have read and accepted the CLA agreement (only required once).

regression is found:

evan

src/core/configuration/DefaultConfig.ts

@@ -336,9 +336,10 @@ export class DefaultConfig implements Config {
   trainSpawnRate(numberOfStations: number): number {
     return Math.min(1400, Math.round(40 * Math.pow(numberOfStations, 0.5)));
   }
-  trainGold(): Gold {
-    return BigInt(4_000);
+  trainGold(isFriendly: boolean): Gold {
+    return isFriendly ? 100_000n : 25_000n;
   }
+
   trainStationMinRange(): number {
     return 15;
   }