Add `Append()` method for `ArrayList`

sources/Data/Collections/ArrayList.uc

@@ -5,7 +5,7 @@
  *  `AcediaObject`s.
  *      Appropriate classes and APIs for their construction are provided for
  *  main primitive types and can be extended to any custom `struct`.
- *      Copyright 2022 Anton Tarasenko
+ *      Copyright 2022-2023 Anton Tarasenko
  *------------------------------------------------------------------------------
  * This file is part of Acedia.
  *
@@ -24,6 +24,7 @@
  */
 class ArrayList extends Collection;
 
+var bool FLAG;
 //  Actual storage of all our data.
 var private array<AcediaObject> storedObjects;
 
@@ -54,6 +55,34 @@ public final function int GetLength()
     return storedObjects.length;
 }
 
+/**
+ *  Appends objects from another `ArrayList` to the caller one.
+ *
+ *  @param  other   Array to append objects from. `none` means nothing will be
+ *      added.
+ *  @return Reference to the caller `ArrayList` to allow for method chaining.
+ */
+public final function ArrayList Append(ArrayList other)
+{
+    local int                   i, shift;
+    local array<AcediaObject>   otherObjects;
+
+    if (other == none)          return self;
+    if (other.GetLength() <= 0) return self;
+
+    shift = storedObjects.length;
+    otherObjects = other.storedObjects;
+    SetLength(storedObjects.length + otherObjects.length);
+    for (i = 0; i < otherObjects.length; i += 1)
+    {
+        if (otherObjects[i] != none) {
+            otherObjects[i].NewRef();
+        }
+        storedObjects[i + shift] = otherObjects[i];
+    }
+    return self;
+}
+
 /**
  *      Changes length of the caller `ArrayList`.
  *      If `ArrayList` size is increased as a result - added items will be