Custom Rokit Manifest Location

Rokit hard-codes manifest file names based on tool compatibility. This basically mandates that your manifest file lives at the root of your project; otherwise, you have to screw around with your cwd every time you want to run Rokit. It would be more suitable if we could pass a flag (`--manifest-file <path/to/rokit.toml>`?) to Rokit to specify where to look for a manifest file. In my case, I want to be able to tuck my manifest file away in a `.config` directory with the rest of my countless config files (git hooks, commit linting, formatting, etc).