feat: client & server behaviours added

Engine.Systems/Network/ClientBehaviour.cs

@@ -0,0 +1,16 @@
+using Engine.Core;
+
+namespace Engine.Systems.Network;
+
+/// <summary>
+/// Basic client behaviour that finds the <see cref="INetworkCommunicatorClient"/> in the universe in it's first active frame.
+/// <br/> 
+/// Disclaimer: It implements <see cref="IFirstFrameUpdate"/> and <see cref="ILastFrameUpdate"/> in virtual methods.
+/// </summary>
+public class ClientBehaviour : Behaviour, IFirstFrameUpdate, ILastFrameUpdate
+{
+    public INetworkCommunicatorClient Client { get; private set; } = null!;
+
+    public virtual void FirstActiveFrame() => Client = Universe.FindRequiredBehaviour<INetworkCommunicatorClient>();
+    public virtual void LastActiveFrame() => Client = null!;
+}

Engine.Systems/Network/ServerBehaviour.cs

@@ -0,0 +1,16 @@
+using Engine.Core;
+
+namespace Engine.Systems.Network;
+
+/// <summary>
+/// Basic server behaviour that finds the <see cref="INetworkCommunicatorServer"/> in the universe in it's first active frame.
+/// <br/> 
+/// Disclaimer: It implements <see cref="IFirstFrameUpdate"/> and <see cref="ILastFrameUpdate"/> in virtual methods.
+/// </summary>
+public class ServerBehaviour : Behaviour, IFirstFrameUpdate, ILastFrameUpdate
+{
+    public INetworkCommunicatorServer Server { get; private set; } = null!;
+
+    public virtual void FirstActiveFrame() => Server = Universe.FindRequiredBehaviour<INetworkCommunicatorServer>();
+    public virtual void LastActiveFrame() => Server = null!;
+}