[Docs] Add a Quick start subpage to Contributing

[weronikaolejniczak]

The purpose of this task is to add a Quick start subpage to the Contributing section in the docs.

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The point is to add a simplified step by step guide for someone who likely doesn't have EUI checked out locally already that explains how to checkout the project, set it up, run docs, make edits, and then create a PR.

Leverage what's already written here: packages/website/README.md

[JasonStoltz]

Just a note:

We have instructions on running EUI website locally in two places already:

• We have content here that describes how to run website.
• And we have similar content here.

I think the idea here would be to have a "Quick Start" guide in the documenting section of our wiki linked from our docs site.

It would be ideal to not have to duplicate the instructions for running website in a 3rd place -- if it's possible, we could link to a separate section for instructions for running website from within this Quick Start guide.