Fix colors in filters widgets

[kele23]

Hi Mendix Team;
I noticed that some colors inside the css of data widget ( datagrid / filters ) are not using css variables.
With the passage of Atlas V4 that is using css variables for color customisation, it will be great if also those widgets can use css variables for colors.

Those are some changes that I had to made to make this widgets to follow the atlas core variables:

.widget-dropdown-filter-state-icon, .widget-dropdown-filter-toggle {
    fill: currentColor;
}

.react-datepicker-time__header, .react-datepicker-year-header, .react-datepicker__current-month {
    color: inherit;
}

.react-datepicker {
    background-color: var(--bg-color-secondary, #FFF);
    color: var(--font-color-default, #000);
    --dg-day-color: var(--font-color-default);
}

.react-datepicker__month-select, .react-datepicker__month-year-select, .react-datepicker__year-select {
    background-color: var(--bg-color-secondary, #FFF);
}

.pagination-bar {
    color: var(--font-color-default, #000);
}

.widget-dropdown-filter-menu {
    --scroll-shadow: var(--bg-color-secondary, #FFF);
}

Is it possible to "include" those inside the widget css? Or better create a dedicated set of variables like the ones that I see for accordion / labels etc..?

Thanks
M