Add events for GunComponent values, muzzle flashes and cartridge spread (#24077)

* Add a modifier event for GunComponent values

* Add docs

* Add VV readwrite to modified values

* Add more docs

* More docs

* Add Gun parameter to GunRefreshModifiersEvent

* Add another event for handling cartridge spread

* Fix pneumatic speed

Content.Shared/PneumaticCannon/PneumaticCannonComponent.cs

@@ -38,6 +38,12 @@ public sealed partial class PneumaticCannonComponent : Component
     [DataField("baseProjectileSpeed")]
     public float BaseProjectileSpeed = 20f;
 
+    /// <summary>
+    ///     The current projectile speed setting.
+    /// </summary>
+    [DataField]
+    public float? ProjectileSpeed;
+
     /// <summary>
     /// If true, will throw ammo rather than shoot it.
     /// </summary>