[BUG] Decimal conversion in toJsonString depends on system locale and uses wrong separator

[ivan-nazarenko]

The json specification requires a "." for decimal separator: https://www.json.org/json-en.html

toJsonString uses "," for decimal separator for some system locales like German or Spanish

Test to reproduce the issue:

import org.junit.jupiter.api.Test;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import static org.junit.jupiter.api.Assertions.assertEquals;

public class DecimalPointFormattingTest {

    @Test
    void formatsNumbersWithDecimalDot() {
        Locale.setDefault(Locale.GERMAN);
        Map fields = new HashMap<String, Object>();
        fields.put("number", 1.1);

        com.beust.klaxon.JsonObject json = new com.beust.klaxon.JsonObject(fields);

        String string = json.toJsonString(false, true);
        assertEquals("{\"number\":1.1E0}", string);
    }

}