One further question: do you know a painless way how you can influence Hugo to add the class="lazyload" to <img> tags automatically, when it renders HTML?
So far I only found a way using shortcodes (which would require to change the way how pictures are referenced in my markdown files). Alternatively I stumbled upon a discussion (Add a class to images) where people described how to add a class to <img> in Markdown. But this didn’t work for me for some reason.