Add ruff linting configuration

[shalgrim]

Ruff is currently running via pre-commit hooks (ruff-check and ruff-format), but there is no explicit ruff configuration in pyproject.toml. This means ruff is running with its default, minimal, ruleset.

Per discussion on #194, a [tool.ruff] section should be added to pyproject.toml with an appropriate set of rules. Toga's configuration (see pyproject.toml) is a reasonable starting point, adapted for this project's needs.

[freakboy3742]

Thanks for logging this.

Out of interest, how did you create the issue? It doesn't follow our standard "new issue" template, which is something we see from time to time, but I've never had anyone explain how they're able to do it - since it shouldn't be possible.

[shalgrim]

Ah thanks for letting me know. I'll fix. I did it with the gh cli.

[freakboy3742]

There's no fix needed - the ticket has captured everything we need in this case. The interest was more about the how (and whether we can prevent it). #196 has just added a caveat to the docs warning that we want people to use the templates, which I think is about as good as we're going to get in this case.