createMainConfigTab example

'font-size-h5' => '@font-size-base',
        'font-size-h6' => 12,
        'panel-header-font-size' => 14,
        'label-font-size' => 14,
        'input-font-size' => 14,
        'btn-font-size' => 14,
        'btn-icon-size' => 10,
    ];

    public function createConfig(TabContainer $container)
    {
        $container->addTab($this->createMainConfigTab());

        $tab = $this->createTab(
            'responsive_tab',
            '__responsive_colors__'
        );
        $container->addTab($tab);

        $tab->addElement($this->createBottomTabPanel());
    }

    /** * Helper function to merge default theme colors with color schemes. */