Add installation/getting started instructions for metal-clay-components

[jbalsas]

Copied over from the old claycss.com repo, opened by @Robert-Frampton:

@Robert-Frampton:

/cc @matuzalemsteles @carloslancha

Currently we have soy code examples for components that have an implementation in https://github.com/metal/metal-clay-components, but no instructions on where those code examples come from, or how to use them.

It would be nice to have a guide on how to get started with metal-clay-components.

@matuzalemsteles:

Yes is important, yesterday, some people were asking me how to use clay on the portal. I think I can work on it with @carloslancha on this.

@brunobasto:

Hey @Robert-Frampton, about using it in portal, are we also documenting the taglib wrappers around Clay components? If so, what's the best place to make that documentation/snippets available?

@Robert-Frampton:

Hey @brunobasto,

In regards to the taglibs, it might make sense to have something in dev.liferay.com? I suppose we could have something here, but because it's something that can only be used in Portal we should probably have it in the developer network.

@brunobasto:

I guess it makes sense to put it there, I was just thinking if we can update it there as fast as we can here, so that our own devs can stay tuned on what's available as we go.

[jbalsas]

Closing in favour of #410