[flat-json-widget] Preserve newline characters in input fields. Issue where newline characters (\n) in input fields were removed when saving via the HTML form. Updated the logic to ensure newline characters are preserved in both display and saved data. Fixed #19

[flat-json-widget] Preserve newline characters in input fields. Issue where newline characters (\n) in input fields were removed when saving via the HTML form. Updated the logic to ensure newline characters are preserved in both display and saved data. Fixed #19 #54