Extracting main UI elements to cerebro-ui package

[KELiON]

I started discussion in #277 and most of the plugin contributors agreed in #280 that it is important to have common UI components as a standalone package for easy reusability.

I've already create repository for that: https://github.com/KELiON/cerebro-ui

Here I'd like to track the progress and discussion.

As I see now, this package should include:

• Form elements (checkbox, text input, radio button, dropdown, labels)
• Loader
• List with keyboard navigation (like in google preview now)
• (ideas what else?)

[ocReaper]

A grid or layout system would be nice, since many plugin use 2 column layout with an image and a description. Also a card-like element could be useful like the one in the brainmaestro/cerebro-stackoverflow plugin.

[lubien]

I think we should learn from mature UI frameworks like Quasar.

Let's take a look at Quasar's list view.

Pretty much covers a lot of common cases in list views like simple lists, lists with icons (at left, right or both sides), lists with dropdown buttons, lists with images...

The Card element is always useful.

Tabs would be great, specially in contexts like settings.

And other minor UI components like form inputs or labels would make the plugin development experience easier :)

[KELiON]

We can move this conversation to cerebro-ui repo. Currently I didn't add new components, just moved what was already implemented.