Allow a value instead of an array of a value.

[matyalatte]

Tuw now allows a value instead of an array of a value in JSON files. You can remove array brackets [] and indentations if an array has only one item.

{
    "gui": {
        "label": "You don't need brackets now!",
        "command": "echo %-%",
        "components": {
            "type": "text",
            "label": "Type 'Hello!'",
            "platforms": "win"
        }
    }
}