Source code for https://victorfont.com/add-snapchat-simple-social-icons/

my_custom_simple_social_default_profiles.php

<?php

add_filter( 'simple_social_default_profiles', 'my_custom_simple_social_default_profiles' );
function my_custom_simple_social_default_profiles() {
    $glyphs = array(
        'bloglovin'     => '&#xe60c;',
        'dribbble'      => '&#xe602;',
        'email'         => '&#xe60d;',
        'facebook'      => '&#xe606;',
        'flickr'        => '&#xe609;',
        'github'        => '&#xe60a;',
        'gplus'         => '&#xe60e;',
        'instagram'     => '&#xe600;',
        'linkedin'      => '&#xe603;',
        'pinterest'     => '&#xe605;',
        'rss'           => '&#xe60b;',
        'snapchat'      => '&#xf2ac;',
        'stumbleupon'   => '&#xe601;',
        'tumblr'        => '&#xe604;',
        'twitter'       => '&#xe607;',
        'vimeo'         => '&#xe608;',
        'youtube'       => '&#xe60f;',
    );
    
    $profiles = array(
        'bloglovin' => array(
            'label'   => __( 'Bloglovin URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-bloglovin"><a href="%s" %s>' . $glyphs['bloglovin'] . '</a></li>',
        ),
        'dribbble' => array(
            'label'   => __( 'Dribbble URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-dribbble"><a href="%s" %s>' . $glyphs['dribbble'] . '</a></li>',
        ),
        'email' => array(
            'label'   => __( 'Email URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-email"><a href="%s" %s>' . $glyphs['email'] . '</a></li>',
        ),
        'facebook' => array(
            'label'   => __( 'Facebook URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-facebook"><a href="%s" %s>' . $glyphs['facebook'] . '</a></li>',
        ),
        'flickr' => array(
            'label'   => __( 'Flickr URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-flickr"><a href="%s" %s>' . $glyphs['flickr'] . '</a></li>',
        ),
        'github' => array(
            'label'   => __( 'GitHub URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-github"><a href="%s" %s>' . $glyphs['github'] . '</a></li>',
        ),
        'gplus' => array(
            'label'   => __( 'Google+ URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-gplus"><a href="%s" %s>' . $glyphs['gplus'] . '</a></li>',
        ),
        'instagram' => array(
            'label'   => __( 'Instagram URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-instagram"><a href="%s" %s>' . $glyphs['instagram'] . '</a></li>',
        ),
        'linkedin' => array(
            'label'   => __( 'Linkedin URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-linkedin"><a href="%s" %s>' . $glyphs['linkedin'] . '</a></li>',
        ),
        'pinterest' => array(
            'label'   => __( 'Pinterest URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-pinterest"><a href="%s" %s>' . $glyphs['pinterest'] . '</a></li>',
        ),
        'rss' => array(
            'label'   => __( 'RSS URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-rss"><a href="%s" %s>' . $glyphs['rss'] . '</a></li>',
        ),
        'snapchat' => array(
            'label'   => __( 'SnapChat URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-snapchat"><a href="%s" %s>' . $glyphs['snapchat'] . '</a></li>',
        ),
        'stumbleupon' => array(
            'label'   => __( 'StumbleUpon URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-stumbleupon"><a href="%s" %s>' . $glyphs['stumbleupon'] . '</a></li>',
        ),
        'tumblr' => array(
            'label'   => __( 'Tumblr URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-tumblr"><a href="%s" %s>' . $glyphs['tumblr'] . '</a></li>',
        ),
        'twitter' => array(
            'label'   => __( 'Twitter URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-twitter"><a href="%s" %s>' . $glyphs['twitter'] . '</a></li>',
        ),
        'vimeo' => array(
            'label'   => __( 'Vimeo URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-vimeo"><a href="%s" %s>' . $glyphs['vimeo'] . '</a></li>',
        ),
        'youtube' => array(
            'label'   => __( 'YouTube URI', 'simple-social-icons' ),
            'pattern' => '<li class="social-youtube"><a href="%s" %s>' . $glyphs['youtube'] . '</a></li>',
        ));
    return $profiles;
}

simple-social-icons.css

.simple-social-icons ul li.social-snapchat a {
	font-family: 'FontAwesome';
}