Make Refined GitHub act sooner with `element-ready` #2604

The browser may display content on screen long before dom-ready, so sometimes content appears for a few seconds before Refined GitHub changes it. This is a bit annoying.

https://github.com/sindresorhus/element-ready can avoid this by acting on elements as soon as they appear in the DOM while the page is still loading/streaming.

GitHub sometimes loads new pages via ajax so we have to listen to both the real dom-ready event and the ajaxed one. We handle this with features.onAjaxedPages

We use element-ready in some features but there's currently no loading mechanism that combines element-ready and ajaxed loads.

Possible solutions

Here's some implementations I thought of.

A new single loading method

feature.init({
    ...,
    load: features.onAjaxedPagesOrWait('selector')
});

Better yet, have a onAjaxedPages version that doesn't wait for dom-ready on the first run and element-ready can be used in the feature itself.

✅ Preferred

feature.init({
    ...,
    load: features.onAjaxedPagesOrInstant
});

A completely new loading API

This would split each event and allow us to combine them in any way, but it's a bit verbose

feature.init({
    ...,
    loadOnAjaxed: true,
    loadAfterElement: 'selector'
});

this means regular features (dom-ready + ajaxed) would have to be declared explicitly:

feature.init({
    ...,
    loadOnDomReady: true,
    loadOnAjaxed: true
});

... other suggestions welcome