Proposal: Release process for Version 1.0

[jeremyfowers]

Problem Statement

Updates to turnkeyml that have breaking, large, or disruptive changes should go through a special release process (ie, not simply a PR into `main). Such updates should be tested against any third-party plugins that are in development in other repos.

Proposal

1. Breaking, large, and disruptive changes should be developed in the canary branch
2. PRs into canary go through the regular PR process, however with the expectation that a subsequent PR is needed to merge from canary into main (and then into the PyPI package).
3. Completed PRs into canary can trigger a package push to TestPyPI if they are tagged with RC*.
4. A TestPyPI package must be distributed to registered third-party plugin developers for review whenever there is a PR from canary to main.

Actions

1. The Version 1.0 development will used the proposed practices above
2. If these practices work out well, they will be enshrined into the contribution guidelines

[jeremyfowers]

1. Use the public API contract (Public API contract  #55) to decide if a change is breaking (major version number changes)
2. Must use the "breaking" label on issues
3. Must have a video meeting with the maintainers to discuss the change
4. Merge main into canary