Add support for language specific toggles #14

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"],
    ]
}

• Determine format (also JSON vs YAML)
• Determine whether language specific toggles inherit from the generic toggles (also deal with overwrites)
• Dig into underlying plugin storage (avoid erasing existing toggles upon update; might want to save the serialized representation instead of the current deserialized one)
• Implement the feature