修复readonly在db、redis存储是无效的问题

src/main/java/org/ssssssss/magicapi/adapter/resource/KeyValueResource.java

@@ -43,6 +43,11 @@ public abstract class KeyValueResource implements Resource {
 		return this.path.endsWith(separator);
 	}
 
+	@Override
+	public boolean readonly() {
+		return this.readonly;
+	}
+
 	@Override
 	public final boolean renameTo(Resource resource) {
 		if(resource.name().equalsIgnoreCase(this.name())){