add-editor-styles.php

/**
 * Sets up theme defaults and registers support for various WordPress features.
 */
function tabor_setup() {
	  // Add support for editor styles.
	  add_theme_support( 'editor-styles' );
  
	// Enqueue editor styles.
	add_editor_style( 'assets/css/style-editor.css' );
}
add_action( 'after_setup_theme', 'tabor_setup' );