Loads the theme’s translated strings.

If the current locale exists as a .mo file in the theme’s root directory, it
will be included in the translated strings by the $domain.

The .mo files must be named based on the locale exactly.

function load_theme_textdomain( $domain, $path = false ) {
	/** @var WP_Textdomain_Registry $wp_textdomain_registry */
	global $wp_textdomain_registry;

	/**
	 * Filters a theme's locale.
	 *
	 * @since 3.0.0
	 *
	 * @param string $locale The theme's current locale.
	 * @param string $domain Text domain. Unique identifier for retrieving translated strings.
	 */
	$locale = apply_filters( 'theme_locale', determine_locale(), $domain );

	$mofile = $domain . '-' . $locale . '.mo';

	// Try to load from the languages directory first.
	if ( load_textdomain( $domain, WP_LANG_DIR . '/themes/' . $mofile, $locale ) ) {
		return true;
	}

	if ( ! $path ) {
		$path = get_template_directory();
	}

	$wp_textdomain_registry->set_custom_path( $domain, $path );

	return load_textdomain( $domain, $path . '/' . $locale . '.mo', $locale );
}