Add support for language specific toggles

[Noorts]

Allow adding toggles to the configuration which are only enabled for files in certain languages.

The following is an example configuration just to get the point across. Of course with an optimal and valid JSON structure (which is backwards compatible with the current structure).

{
    "default": [
        ["byte", "short", "int", "long", "float", "double"],
        ["String", "Character"],
    ],
    "java": [
        ["public", "private", "protected"],
        ["class", "interface"],
        ["extends", "implements"],
        ["import", "export"],
    ],
    "js, jsx, ts, tsx": [
        ["const", "let", "var"],
    ]
}

See the shifter plugin for inspiration.