Added configurable weapons.

AlientAttack.MonoGame/Things/Weapons/WeaponState.cs

@@ -0,0 +1,8 @@
+namespace AlienAttack.MonoGame.Things.Weapons;
+
+public sealed class WeaponState
+{
+    public int FireThreshold { get; set; }
+    public float SpeedMultiplier { get; set; } = 1f;
+    public int DamageBonus { get; set; } = 0;
+}