add(1521) - Add nix flake, justfile, and direnv

[dboitnot]

Resolve #1521 - Add nix flake, justfile, and direnv

PR Checklist

• [ ] Wrote a good commit message & description [see guide below].
• [ ] Commit message starts with [Resolve #issue-number].
• [ ] Added/Updated unit tests.
• [ ] Added/Updated integration tests (if applicable).
• [ ] All unit tests (poetry run tox) are passing.
• [ ] Used the same coding conventions as the rest of the project.
• [ ] The new code passes pre-commit validations (poetry run pre-commit run --all-files).
• [ ] The PR relates to only one subject with a clear title. and description in grammatically correct, complete sentences.

Approver/Reviewer Checklist

• [ ] Before merge squash related commits.

Other Information

Guide to writing a good commit

[alex-harvey-z3q]

If this improves the developer experience for @dboitnot and helps him contribute, that would be of a large benefit to the project. I vote to approve this one.

[alex-harvey-z3q]

I am closing this as it appears we have lost Dan again!