added encode_nbt, added 'nbt' and 'nbt_merge' to modify entity API.

src/main/java/carpet/script/value/StringValue.java

@@ -1,5 +1,8 @@
 package carpet.script.value;
 
+import net.minecraft.nbt.StringTag;
+import net.minecraft.nbt.Tag;
+
 public class StringValue extends Value
 {
     private String str;
@@ -30,4 +33,10 @@ public class StringValue extends Value
     {
         return "string";
     }
+
+    @Override
+    public Tag toTag(boolean force)
+    {
+        return StringTag.of(str);
+    }
 }