(docs) Add a "slowstart"

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| Requesting a new feature
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**Proposal/Feature-request:** Approachable starter docs for non-technical/inexperienced folks to get up and running.

I was having dinner with a non-technical designer person and they mentioned they were having quite a bit of trouble getting the basic examples to work -- the "quickstart" commands in particular were intimidating/confusing. There was also confusion about when to open Sketch and how all the commands/pieces fit together. They got snared/blocked on some pretty uninteresting issues.

Rather than pollute the root README with a bunch of instructions, a better approach seems to be to enhance the docs/examples.md with a bit more hand holding so a confused user can get the concept and reach a good jumping off point.

If approved, there'd be both a quickstart for those who get it + a slow start for those who need it

Read docs/examples.md and review the existing quickstart commands and basic examples. Add a more approachable slow-start path that explains how the commands and pieces fit together, including when to open Sketch; done means an inexperienced user can reach a working starting point without changing the root README.

Written by the indexing model from the issue text.