Add debug description & make sparse set arrays œusableFromInline

Sources/FirebladeECS/Nexus.swift

@@ -99,3 +99,10 @@ extension Nexus {
         delegate?.nexusRecoverableErrorOccurred(message)
     }
 }
+
+// MARK: - CustomDebugStringConvertible
+extension Nexus: CustomDebugStringConvertible {
+    public var debugDescription: String {
+        return "Nexus<Entities:\(numEntities) Components:\(numComponents) Families:\(numFamilies)>"
+    }
+}

Sources/FirebladeECS/UnorderedSparseSet.swift

@@ -14,8 +14,8 @@ open class UnorderedSparseSet<Element>: MutableCollection, RandomAccessCollectio
         public let element: Element
     }
 
-    public private(set) var dense: ContiguousArray<Entry>
-    public private(set) var sparse: [Index: Key]
+    @usableFromInline var dense: ContiguousArray<Entry>
+    @usableFromInline var sparse: [Index: Key]
 
     public init() {
         sparse = [Index: Key]()