add StringConverter

Author: HSGamer

storage/simple/src/main/java/me/hsgamer/topper/storage/simple/converter/StringConverter.java

@@ -0,0 +1,9 @@
+package me.hsgamer.topper.storage.simple.converter;
+
+import java.util.function.Function;
+
+public class StringConverter extends SimpleValueConverter<String> {
+    public StringConverter(String valueName, boolean isStringNative, int stringMaxLength) {
+        super(Function.identity(), Function.identity(), valueName, isStringNative, stringMaxLength);
+    }
+}