Create a WooCommerce size guide shortcode

wc-size-guide-shortcode.php

<?php
/**
 * Only copy opening php tag if needed
 * Creates a [wc_size_guide] shortcode
 */
function sww_wc_size_guide_shortcode() {

	ob_start();

	// Paste your table data inside the "echo" (replace the <table> stuff here with your table HTML)
	echo '
		<table class="wc-size-chart">...</table>
	';

	return ob_get_clean();
}
add_shortcode( 'wc_size_guide', 'sww_wc_size_guide_shortcode' );