(new): JSON HTML escaping control

- add Formatter.JSONEscapeHTML and SetJSONEscapeHTML to let JSON writers preserve HTML-sensitive characters when needed while keeping escaping enabled by default.
- switch JSON output to json.Encoder, preserve existing Print/Println newline semantics, and cover the new escaping behavior in tests.

examples/main.go

@@ -32,6 +32,7 @@ func main() {
 	jsonFormatter := sneklog.NewFormatter().
 		SetFormat("[%L] [%N] %m").
 		SetColorOutput(false).
+		SetJSONEscapeHTML(false).
 		SetTimeStampFormat(sneklog.Kitchen)
 
 	textStdout.SetFormatter(formatter)
@@ -62,6 +63,7 @@ func main() {
 		externalJSON,
 	)
 
+	logger.Infoln("Тест <>&")
 	logger.Infoln("service started")
 	logger.Warnln("cache miss")
 	logger.Errorln("request failed")