add plusAssign(family) to MutableEntityBag

src/commonMain/kotlin/com/github/quillraven/fleks/collection/entityBag.kt

@@ -3,6 +3,7 @@
 package com.github.quillraven.fleks.collection
 
 import com.github.quillraven.fleks.Entity
+import com.github.quillraven.fleks.Family
 import kotlin.math.max
 import kotlin.math.min
 import kotlin.random.Random
@@ -470,6 +471,13 @@ class MutableEntityBag(
         entities.forEach { plusAssign(it) }
     }
 
+    /**
+     * Adds all entities of the [family] to the bag. If the [capacity] is not sufficient then a resize is happening.
+     */
+    operator fun plusAssign(family: Family) {
+        family.entities.forEach { plusAssign(it) }
+    }
+
     /**
      * Removes all [entities] of the bag.
      */

src/commonTest/kotlin/com/github/quillraven/fleks/collection/EntityBagTest.kt

@@ -1,6 +1,7 @@
 package com.github.quillraven.fleks.collection
 
 import com.github.quillraven.fleks.Entity
+import com.github.quillraven.fleks.Family
 import com.github.quillraven.fleks.configureWorld
 import kotlin.test.*
 
@@ -661,6 +662,22 @@ class EntityBagTest {
         assertTrue { testEntity2 in bag }
     }
 
+    @Test
+    fun `test plusAssign of a family`() {
+        val bag = mutableEntityBagOf()
+        val testWorld = configureWorld { }
+        val toAdd = Family(world = testWorld).apply {
+            onEntityAdded(testEntity1, BitArray())
+            onEntityAdded(testEntity2, BitArray())
+        }
+
+        bag += toAdd
+
+        assertEquals(2, bag.size)
+        assertTrue { testEntity1 in bag }
+        assertTrue { testEntity2 in bag }
+    }
+
     @Test
     fun `test minusAssign of an EntityBag`() {
         val bag = mutableEntityBagOf()