Themable Input

As a user
I can enter text into a field
so I can provide information to the application

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**Dev notes**

This will be our first themable component. Let's make this one match the HTML input API as much as possible—no bells, no whistles! No labels, no icons, nothing fancy. Just the input. It will take its presentational values from the theme data.

**Acceptance**
- [x] Input should draw its styles from the theme data and support available themes.
- [x] Input should support all props a standard react `input[type=text]` component supports. All event handlers, `disabled`, `readonly`, etc. Use react docs and MDN to find the full list.
- [x] Input should support "line" and "box" style as well as an undecorated version with no box or line.

**Todo**
- [x] Test presenters - snapshots
- [x] Test presenters - gemini
- [x] Test behaviors - unit tests
- [x] Test composer i.e. `Input` - Combo of unit and integration tests
- [x] Add/update storybook
- [ ] Document public prop types & docgen info
- [ ] Check readme, add examples