[BPK-2269] Add theme attributes render prop component

[k0nserv]

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[shaundon]

Diff lgtm, just gonna run it locally.

[shaundon]

Having a code sample is a great move - we should do this more in other PRs really!

[shaundon]

Works great locally - nice one 🎉

[tiagoengel]

Not sure I understand the advantage of this approach instead of just a function to read the property. I'm not a big fan of HOCs, specially because here we can have withPrimaryColor and withTheme together, that's a bit unecessary IMO.

If we have withTheme already I think we should just use that and provide a simple function that reads from it. I believe the fact that users will have to wrap the component with withTheme is not a big deal as the function will require the theme, and that would make it clear wrapping is required.

Another point is that this approach is not very flexible, adding a secondaryColor would be a lot more complex.

[k0nserv]

I agree on your point about secondaryColor the reason we are going for this over just a function where the consumer can pass the theme prop from withTheme and have the function extract the primary color. The HOC is preferable over this method because:

1. Consumer has to do less work hence there's less risk to do it incorrectly.
2. We maintain abstraction and can change how we do theming without consumers having to care since they are not directly using withTheme

[k0nserv]

Pushed render prop version in 4c8784f

[tiagoengel]

Just one comment. LGTM otherwise

[matthewdavidson]

Otherwise LGTM

[matthewdavidson]

Suggested change

	- Added a new Render Prop component `BpkThemeAttributes` to support arbitrary usage of a theme's `primaryColor` attribute. If rendered outside of a `BpkThemeProvider` with a defined theme `colorBlue500` is used instead.
	- Added a new [Render Prop](https://reactjs.org/docs/render-props.html) component `BpkThemeAttributes` to support arbitrary usage of a theme's `primaryColor` attribute. If rendered outside of a `BpkThemeProvider` with a defined theme `colorBlue500` is used instead.