Add Spectre Components

Add "Components" from Spectre, stories and tests for them:

* ~~Accordions~~
* Autocomplete
* ~~Avatars~~
* Badges
* Bars
* Breadcrumbs
* ~~Cards~~
* ~~Chips~~
* Empty states
* Menus
* ~~Modals~~
* ~~Navs~~
* Pagination
* Panels
* ~~Popovers~~
* Steps
* Tabs
* ~~Tiles~~
* Toasts
* Tooltips

1. Create an issue "Add component {ComponentName}" and state that you're working on it.

2. Follow the same code style as other components:
* Use Standard JS style
* Use component layout described in the readme and as seen in other component files

3. Make a pull request following the [PR template](https://github.com/CodeDraken/spectre-react/blob/master/PULL_REQUEST_TEMPLATE.md) and add a reference to the issue.

https://picturepan2.github.io/spectre/components.html

Inizia leggendo il README del repository e ispezionando i file dei componenti esistenti per comprendere il layout e lo stile Standard JS. Scegli un componente Spectre non ancora completato, crea la relativa issue separata come richiesto, quindi aggiungi il componente, le stories e i test e usa il template della PR quando invii la pull request.

Scritto dal modello di indicizzazione a partire dal testo della issue.