[CI] - Test with OpenTofu

After verifying compatibility, or updating PyTerraBackTYL to be compatible with OpenTofu (see Issue #54), update CI to include a second `matrix` that validates against commonly used versions of OpenTofu.

https://github.com/dev-dull/PyTerraBackTyl/blob/3f2e78138f356eb31e83c51e254c048fe8c3da45/.github/workflows/docker-build.yaml#L65C1-L65C30