Add a placeholder to the navigation search

gistfile1.txt

add_action( 'after_setup_theme','tu_change_nav_placeholder' );
function tu_change_nav_placeholder()
{
	remove_action( 'generate_inside_navigation','generate_navigation_search');
	add_action( 'generate_inside_navigation','tu_navigation_search', 5 );
}

function tu_navigation_search()
{	
	if ( function_exists( 'generate_get_setting' ) && 'enable' !== generate_get_setting( 'nav_search' ) )
		return;
			
	?>
	<form method="get" class="search-form navigation-search" action="<?php echo esc_url( home_url( '/' ) ); ?>">
		<input type="search" placeholder="YOUR PLACEHOLDER HERE" class="search-field" value="<?php echo esc_attr( get_search_query() ); ?>" name="s" title="<?php _ex( 'Search', 'label', 'generatepress' ); ?>">
	</form>
	<?php
}