Make fuel tanks explodey again (#4670)

* make fuel tanks explodey again

* tanks now take damage from lit welders,

Content.Server/Destructible/Thresholds/Behaviors/ExplodeBehavior.cs

@@ -0,0 +1,21 @@
+using Content.Server.Explosion;
+using Content.Server.Explosion.Components;
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+using Robust.Shared.Serialization.Manager.Attributes;
+
+namespace Content.Server.Destructible.Thresholds.Behaviors
+{
+    /// <summary>
+    ///     This behavior will trigger entities with <see cref="ExplosiveComponent"/> to go boom.
+    /// </summary>
+    [UsedImplicitly]
+    [DataDefinition]
+    public class ExplodeBehavior : IThresholdBehavior
+    {
+        public void Execute(IEntity owner, DestructibleSystem system)
+        {
+            owner.SpawnExplosion();  
+        }
+    }
+}