Add Focus Widget values to Session Settings

[retiutut]

Problem

Just noticed that this was not added to Session Settings when re-implemented.

Expected

Save/Load/Default dropdowns for the Focus Widget

Operating System and Version

All OS

GUI Version

v6.0.0-beta.0

Are you running the downloaded app or from Processing/VSCode?

Both

Type of OpenBCI Board

All boards and modes

Console Log and Screenshots

    private final String kJSONKeyDataInfo = "dataInfo";
    private final String kJSONKeyTimeSeries = "timeSeries";
    private final String kJSONKeySettings = "settings";
    private final String kJSONKeyFFT = "fft";
    private final String kJSONKeyAccel = "accelerometer";
    private final String kJSONKeyNetworking = "networking";
    private final String kJSONKeyHeadplot = "headplot";
    private final String kJSONKeyBandPower = "bandPower";
    private final String kJSONKeyWidget = "widget";
    private final String kJSONKeyVersion = "version";
    private final String kJSONKeySpectrogram = "spectrogram";
    private final String kJSONKeyEmg = "emg";
    private final String kJSONKeyEmgJoystick = "emgJoystick";
    private final String kJSONKeyMarker = "marker";

^^^No key exists for Focus Widget and the values are private in the class 👎