Remove image width and height declaration in WordPress

remove_wp_width_height.php

//add to functions.php 
//remove inline width and height added to images
  add_filter( 'post_thumbnail_html', 'remove_thumbnail_dimensions', 10 );
	add_filter( 'image_send_to_editor', 'remove_thumbnail_dimensions', 10 );
	// Removes attached image sizes as well
	add_filter( 'the_content', 'remove_thumbnail_dimensions', 10 );
	function remove_thumbnail_dimensions( $html ) {
    		$html = preg_replace( '/(width|height)=\"\d*\"\s/', "", $html );
    		return $html;
	}