Add item DataComponent implements (part 2)

level/component/mapid.go

@@ -0,0 +1,14 @@
+package component
+
+import pk "github.com/Tnze/go-mc/net/packet"
+
+var _ DataComponent = (*MapID)(nil)
+
+type MapID struct {
+	pk.VarInt
+}
+
+// ID implements DataComponent.
+func (MapID) ID() string {
+	return "minecraft:map_id"
+}