Easy wordpress social media icons, simply add an index to the theme_name_get_social_opts array and a everything to get it showing is handled.

customizer.php

<?php
if ( ! function_exists( 'theme_name_theme_customize_register' ) ) {
	/**
	 * Register individual settings through customizer's API.
	 *
	 * @param WP_Customize_Manager $wp_customize Customizer reference.
	 */
	function theme_name_theme_customize_register( $wp_customize ) {
		$wp_customize->add_section(
			'theme_name_contact',
			array(
				'title'    => __( 'Contact and social media settings', 'theme_name' ),
				'priority' => 10,
			)
		);

		$opts = theme_name_get_social_opts();
		for ( $i = 0; $i < count( $opts ); $i++ ) {
			$wp_customize->add_setting(
				'theme_name_' . $opts[ $i ]['name'],
				array(
					'default' => null,
				)
			);

			$wp_customize->add_control(
				'theme_name_' . $opts[ $i ]['name'],
				array(
					'label'   => sprintf( '%s ' . __( 'link', 'theme_name' ), $opts[ $i ]['name'] ),
					'section' => 'theme_name_contact',
					'type'    => 'url',
				)
			);
		}
	}
}
add_action( 'customize_register', 'theme_name_theme_customize_register' );

functions.php

<?php
if ( ! function_exists( 'theme_name_get_social_opts' ) ) {
	/**
	 * Add to the array to add another social link
	 */
	function theme_name_get_social_opts() {
		return array(
			array(
				'name'         => 'instagram',
				'icon-classes' => 'fa fa-instagram',
			),
			array(
				'name'         => 'twitter',
				'icon-classes' => 'fa fa-twitter',
			),
			array(
				'name'         => 'facebook',
				'icon-classes' => 'fa fa-facebook',
			),
			array(
				'name'         => 'youtube',
				'icon-classes' => 'fa fa-youtube-play',
			),
		);
	}
}

if ( ! function_exists( 'theme_name_get_social_links' ) ) {
	/**
	 * Return the social links that are defined in the customizer.
	 */
	function theme_name_get_social_links() {
		$available = theme_name_get_social_opts();
		$return    = array();
		for ( $i = 0; $i < count( $available ); $i++ ) {
			$user_input = get_theme_mod( 'theme_name_' . $available[ $i ]['name'] );
			if ( strlen( $user_input ) > 0 ) {
				$entry = [
					'icon-classes' => $available[ $i ]['icon-classes'],
					'url'          => $user_input,
				];
				array_push( $return, $entry );
			}
		}
		return $return;
	}
}

sample-implementation.php

<div class="footer-row-2 w-100 mx-md-5 mt-3 d-flex justify-content-center">
  <?php
  $socials = theme_name_get_social_links();
  ?>
  <div class="footer-icons my-4 d-flex">
    <?php
    for ( $i = 0; $i < count( $socials ); $i++ ) : ?>
      <a href="<?php echo esc_url( $socials[ $i ]['url'] ); ?>" class="bg-white mx-3 text-center d-block">
        <i class="py-2 fa-2x <?php echo esc_attr( $socials[ $i ]['icon-classes'] ); ?>"></i>
      </a>
    <?php endfor; ?>
  </div>
</div>