docs: Improve IF cmd execution docs (#2405)

Adds samples and better explains workflow.

docs/guides/int_framework/samples/intro/event.cs

@@ -0,0 +1,14 @@
+// Theres multiple ways to subscribe to the event, depending on your application. Please use the approach fit to your type of client.
+// DiscordSocketClient:
+_socketClient.InteractionCreated += async (x) =>
+{
+    var ctx = new SocketInteractionContext(_socketClient, x);
+    await _interactionService.ExecuteCommandAsync(ctx, _serviceProvider);
+}
+
+// DiscordShardedClient:
+_shardedClient.InteractionCreated += async (x) =>
+{
+    var ctx = new ShardedInteractionContext(_shardedClient, x);
+    await _interactionService.ExecuteCommandAsync(ctx, _serviceProvider);
+}