Create tables during plugin activation

According to https://codex.ww.wp.xz.cn/Creating_Tables_with_Plugins plugins should create tables during plugin activation.

However, this plugin doesn’t do that.

In lib/class-wp-smush-dir.php, create_table() creates the table. This function starts with:

// Run the query only on directory smush page.
if ( ! isset( $_GET['page'] ) || 'smush' !== $_GET['page'] ) {
        return null;
}

I suggest that, in order to comply with WordPress best practices:
1. A call to register_activation_hook be added which calls create_table()
2. The if condition checking the page be removed from create_table()
3. All other calls to create_table be removed