Landing page plugin boilerplate for Wordpress

landingpage.php

<?php
/**
 * Plugin Name: Landingpage
 * Plugin URI: https://site.com/landingpage
 * Description: A landingpage plugin
 * Version: 1.0.0
 * Author: Author
 * Author URI: author.com
 * License: GPL2
 */

if ( !is_admin() ) {

    add_action('template_redirect','landingpage_2018'); //Fires before determining which template to load.
    function landingpage_2018(){
        // Enqueue styles and scripts for our plugin. Add class name to body of the template page.
        if ( is_page('landingpage') ) {
            add_action( 'wp_enqueue_scripts', 'landingpage_enqueued_assets' );
            function landingpage_enqueued_assets() {
                wp_enqueue_script( 'landingpage_script', plugin_dir_url( __FILE__ ) . 'dist/js/script.min.js', array( 'jquery' ), filemtime(plugin_dir_path( __FILE__ ) . 'dist/js/script.min.js') , true );
                wp_enqueue_style( 'landingpage_style', plugin_dir_url( __FILE__ ) . 'dist/css/style.min.css', array(), filemtime(plugin_dir_path( __FILE__ ) . 'dist/css/style.min.css') );
            }

            add_filter( 'body_class', 'landingpage_class_names' );
            function landingpage_class_names( $classes ) {
                $classes[] = 'landingpage';
                return $classes;
            }
        }
    }

    // Set the template for the page
    add_filter( 'page_template', 'landingpage_page_template' );
    function landingpage_page_template( $page_template ) {
        if ( is_page( 'landingpage' ) ) {
            $page_template = plugin_dir_path( __FILE__ ). '/landingpage-template.php';
        }
        return $page_template;
    }
}