Demo pre-release workflow is broken

[mciantyre]

See here. It hasn't generated any pre-releases, as expected.

I'm re-thinking this pre-release job. It's going to result in us having many, many releases. I'll probably remove it, rather than fix it.

Instead, I'll add a workflow to package our specific, intended releases. It should work like this:

• Eric crates a release on his computer, or through GitHub. He assigns a tag, like v0.1.2, to the release.
  • Edit: I can't easily figure-out how to trigger automatic builds from the releases page. We'll instead push git tags from one of our local machines.
• A workflow runs, building all the demos and binaries.
• A workflow publishes it to the release page as a full release (not a pre-release).

We can do these after specific, notable milestones in development.

We could also do this building manually, but it's less error-prone to have an automated system do it for us.

[mciantyre]

Created a test release, v0.0.0-test0, and the new workflow worked. See the [releases page] for the output.

[mciantyre]

Here is the successful job!