Add mountains to the grid

.gradle/8.10.2/executionHistory/executionHistory.bin

.gradle/8.10.2/executionHistory/executionHistory.lock

.gradle/8.10.2/fileHashes/fileHashes.bin

.gradle/8.10.2/fileHashes/fileHashes.lock

.gradle/8.10.2/fileHashes/resourceHashesCache.bin

.gradle/buildOutputCleanup/buildOutputCleanup.lock

build/classes/java/main/app/SimulatorApplication.class

build/classes/java/main/controller/Controller.class

build/classes/java/main/model/BoardElement.class

build/classes/java/main/model/BoardFireFighterBehavior.class

build/classes/java/main/model/FirefighterBoard.class

build/tmp/compileJava/previous-compilation-data.bin

src/main/java/app/SimulatorApplication.java

src/main/java/controller/Controller.java

src/main/java/model/BoardElement.java

src/main/java/model/BoardFireFighterBehavior.java

src/main/java/model/FirefighterBoard.java

src/main/java/model/MotorizedFireFighter.java

src/main/java/model/Mountain.java

src/main/java/model/Terrain.java