Logger and log file

We need to log errors and such to a file instead/aswell as the console.

Currently, things like uncategoriseable queries will be spat out to the console but that's only if sql-lint is used via the command line. If it's used through an editor (like neovim or vscode), these warnings will not show.

For userspace programs like sql-lint it looks like the "correct" place to put them is `~/.cache/sql-lint/logs/my-loghere.log`.

This follows the XDG spec.