Add Featured Image Column to Posts List

<?php
add_filter( 'manage_posts_columns', 'scseed_add_thumbnail_column' );
function scseed_add_thumbnail_column( $columns ) {
    $new = array();
    foreach ( $columns as $key => $value ) {
        if ( 'title' === $key ) {
            $new['scseed_thumb'] = __( 'Image' );
        }
        $new[ $key ] = $value;
    }
    return $new;
}

add_action( 'manage_posts_custom_column', 'scseed_render_thumbnail_column', 10, 2 );
function scseed_render_thumbnail_column( $column_name, $post_id ) {
    if ( 'scseed_thumb' !== $column_name ) {
        return;
    }
    if ( has_post_thumbnail( $post_id ) ) {
        echo get_the_post_thumbnail( (int) $post_id, array( 60, 60 ) );
    } else {
        echo '<span aria-hidden="true">&#8212;</span>';
    }
}

add_action( 'admin_head', 'scseed_thumbnail_column_style' );
function scseed_thumbnail_column_style() {
    $screen = get_current_screen();
    if ( $screen && 'edit-post' === $screen->id ) {
        echo '<style>.column-scseed_thumb{width:70px;}</style>';
    }
}