Bring Your Own Link/Button/Icon

[mkrause]

We frequently use basic components like Link, Button, or Icon inside of other components. We currently don't have a standard way to override/customize these components. For example:

• Link – Consumers will likely want to override this to hook it up to their router library (see also Bring Your Own Router #126). Or turn it into a Button instead.
• Button – Consumers may want to customize the behavior of the Button, or turn it into a Link instead.
• Icon – A lot of components will have an icon prop which allows the user to select an icon from Baklava's own icon pack. But what if the consumer wants to use a custom icon that's not in the icon pack?
  • Idea: we could just allow users to inject their SVG sprites into the document under some global ID (maybe prefixed to avoid name clashes). Then, we wouldn't need users to actually inject a custom component, instead they could just keep using <Icon/> and it will load the custom SVG sprites. If we convert IconName into a TypeScript interface then type checking can be done through interface extension.