Add tags api

registry/registry.go

@@ -1,5 +1,7 @@
 package registry
 
+import "slices"
+
 type Registry[E any] struct {
 	keys    map[string]int32
 	values  []E
@@ -47,6 +49,16 @@ func (r *Registry[E]) Put(name string, data E) (id int32, val *E) {
 	return
 }
 
+// Tags
+
+func (r *Registry[E]) Tag(tag string) []*E {
+	return slices.Clone(r.tags[tag])
+}
+
+func (r *Registry[E]) ClearTags() {
+	r.tags = make(map[string][]*E)
+}
+
 // func (r *Registry[E]) BindTags(tag string, ids []int32) error {
 // 	values := make([]*E, len(ids))
 // 	for i, id := range ids {