document new global concept about imba.io

[trafnar]

here's where it was described: https://www.youtube.com/watch?v=0uWqAi9hMVw&t=760s

basic idea is you can add a <global> tag into your template anywhere and event listeners on that will be global to the whole window, and children will be appended to the end of the body.

<global keypress=handleKeypressFromAnywhere>

<global>
    <div> "some content, maybe a modal"

[trafnar]

This is live here: https://imba.io/tags/custom-components#the-global-tag