getIconExt(icon) {
        const blogIcon = icon || this.settingsCache.get('icon');

        // If the native format is supported, return the native format
        if (blogIcon.match(/.ico$/i)) {
            return 'ico';
        }

        if (blogIcon.match(/.jpe?g$/i)) {
            return 'jpeg';
        }

        if (blogIcon.match(/.png$/i)) {
            return 'png';
        }

        // Default to png for all other types
        return 'png';
    }
We support the usage of .svg, .gif, .webp extensions, but (for now, until more browser support them) transform them to 
a simular extension
@param {string} [icon]
@returns {'png' | 'ico' | 'jpeg'}