getCustomThemeCard = () => {
    var propertiesContainer = document.createElement('form');
    const keys = Object.keys(customTheme);
    keys.forEach((key) => {
        const property = document.createElement('div');
        const newPropertyLabel = document.createElement('label');
        newPropertyLabel.textContent = `${key} (${customTheme[key].description})`;
        newPropertyLabel.setAttribute('for', key);
        const newPropertyInput = document.createElement('input');
        newPropertyInput.setAttribute('type', 'color');
        newPropertyInput.setAttribute('name', key);
        newPropertyInput.setAttribute('value', customTheme[key].color);
        newPropertyInput.classList.add('customColorInput');
        property.append(newPropertyLabel);
        property.append(newPropertyInput);
        propertiesContainer.append(property);
    });
    const downloadAnchor = document.createElement('a');
    downloadAnchor.setAttribute('id', 'downloadThemeFile');
    downloadAnchor.setAttribute('style', 'display:none');
    propertiesContainer.appendChild(downloadAnchor);
    return propertiesContainer;
}
Generates Custom theme card HTML
return Html Element Theme card html (properties_container)