How about the ability to include HTML code that's in another file or link? I'm surprised that such a basic modularity mechanism still isn't in the HTML standard.
Some links: https://w3c.github.io/webcomponents/spec/imports/ https://www.html5rocks.com/en/tutorials/webcomponents/import...
Not sure about the current support in browsers, but the specification is currently a draft
https://www.html5rocks.com/en/tutorials/webcomponents/import... https://caniuse.com/#feat=imports