Support tsp init of Playground samples

To address the following user feedback on `tsp init`:

- I was expecting the TypeSpec files to contain TypeSpec code, but they were empty. I had to figure out from combination of docs/playground/GitHub repo what a basic TypeSpec API would look like.
- What’s the “Hello, World Console App Template” equivalent for TypeSpec?

we should consider making the playground examples available through tsp init. This would short-cut the process this user wound up using -- selecting an example in the playground and copy/pasting this into a newly created TypeSpec project.