add player package with key client-side player functionality, update protocol codecs, and refactor metadata definitions and slot usage

pkg/game/inventory/event.go

@@ -0,0 +1,13 @@
+package inventory
+
+import "github.com/Tnze/go-mc/chat"
+
+type ContainerOpenEvent struct {
+	WindowID int32
+	Type     int32
+	Title    chat.Message
+}
+
+func (c ContainerOpenEvent) EventID() string {
+	return "inventory:container_open"
+}