Bring back an example recipe to start from

[rabernat]

This repo now has no example template to start from

[cisaacstern]

Noting that the pangeo-forge GitHub App will automatically delete any subdirectories merged to recipes/, so once a PR for this example is ready to go, an organization admin will need to temporarily suspend the app installation before merge, here:

https://github.com/organizations/pangeo-forge/settings/installations/28971742

Of course, the GitHub App installation will need to be reinstated immediately after the PR is merged.

Also, it's probably worth considering how this example will relate to the Sandbox's example files (which have likely gone somewhat stale at this point). Potentially the Sandbox example files could be removed (I'm not certain that they are really used). But learning from the example there, we'll probably want some type of automated testing associated with the example here, to ensure that the meta.yaml remains in-spec (and references the latest release of pangeo-forge-recipes), and that the recipe.py is compatible with the latest release of pangeo-forge-recipes. The former requirement points to another issue, which is that we need a JSON Schema for meta.yaml.