Add 1.21.1 chat support (#284)

Merge this without verification. Otherwise can't be reviewed in the further updates.

chat/nbtmessage_test.go

@@ -0,0 +1,36 @@
+package chat_test
+
+import (
+	"testing"
+
+	"github.com/Tnze/go-mc/chat"
+	en_us "github.com/Tnze/go-mc/data/lang/en-us"
+	"github.com/Tnze/go-mc/nbt"
+)
+
+func TestMessage_UnmarshalJSON_string(t *testing.T) {
+	snbts := []string{
+		"{translate: sleep.players_sleeping, with: [I; 1, 37]}",
+	}
+
+	texts := []string{
+		"1/37 players sleeping",
+	}
+
+	chat.SetLanguage(en_us.Map)
+	for i, v := range snbts {
+		bytes, err := nbt.Marshal(nbt.StringifiedMessage(v))
+		if err != nil {
+			t.Errorf("Invalid SNBT: %v", err)
+			continue
+		}
+
+		var cm chat.Message
+		if err := nbt.Unmarshal(bytes, &cm); err != nil {
+			t.Error(err)
+		}
+		if str := cm.String(); str != texts[i] {
+			t.Errorf("gets %q, wants %q", str, texts[i])
+		}
+	}
+}