Thinking about migrating the Apollo Example. But unsure as to what the recommendation is for async rendering of items. Having read, #186 and noticing that all of the new hooks take items as an argument.

What are your thoughts on comboboxes with async items?

Thanks!

Issue description

I've came across a proptype warning when passing an int as options key.
focusItem is declared as a string in App.js seems reasonable enough so i think a simple conversion is enough as a think many people may try to pass an int as the option key, my case was passing the product_id from a an api.

I know that this is against the PropTypes use but i think an exception he

This issue has come up multiple times (#71, #69, #64, etc). Time to add some examples to the docs.

The aria-label currently used is hardcoded directly in template:

https://github.com/vaadin/vaadin-combo-box/blob/7432675574b5395dab5dca9fe99de9fcc8a2447d/src/vaadin-combo-box.html#L66

This is a violation of AA Criteria of WCAG if used on a page with lang != en.

The value of the aria-label has to be configurable by the developer for i18