html code is plain text, you should encounter no problem by send it copy and paste directly. I am not sure if WhatsApp will transfer UTF code into character in some case, if you want to play safe, send it as a .txt file instead.
You want to send the HTML code or the webpage? If you want to send the page, just keep it as HTML file and send it through WhatsApp. If you wish to have a URL link for your page, that is another long story.